Detailed working notes on Higher Airspace Operations (HAO) — the emerging ICAO concept for civil aviation above FL600. This folder expands the summary in topics/hao.md into per-aspect files so each can be read independently.

Files in this folder#

• overview.md — what HAO is, the altitude regime, vehicle taxonomy, and where it sits in the ICAO/ATM framework.
• components.md — the building blocks: vehicle classes, airspace regime, cooperative traffic management services, and the transition corridor.
• blocks.md — regime layers and maturity phases from current controlled airspace through transition to full HAO.
• threads.md — functional axes: traffic management concept, cooperative services, transition through controlled airspace, vehicle certification, C2 spectrum, international coordination.
• modules.md — anatomy of one worked strand: a HAPS climb/descent transition through controlled airspace and the ETM cooperative deconfliction cycle.
• enablers.md — CNS, spectrum, certification, training, regulation, and institutional arrangements.
• performance_objectives.md — KPAs, KPIs, and performance frameworks for HAO operations.
• timeline.md — historical milestones from early HAPS flights through FAA ETM ConOps and the ICAO A41-9 mandate.
• references.md — consolidated ICAO, FAA, EASA, and EUROCONTROL references.

Reading order#

Start with overview.md to understand the concept and its boundaries, then components.md for the building blocks, blocks.md for the maturity progression, and threads.md for the functional axes. Use modules.md for worked examples, enablers.md for the dependency chain, and performance_objectives.md for the measurement framework. timeline.md provides date context; references.md consolidates citations.

Source basis#

Content is grounded in:

• ICAO Doc 10184 (41st Assembly Resolutions), Resolution A41-9 — New Entrants mandate covering HAO and UTM.
• ICAO Annex 11 (Air Traffic Services), §2.11.4 — upper airspace FIR recommendation.
• ICAO Annex 2 (Rules of the Air), §3.3.1.4 and Appendix 3 — cruising levels above FL410.
• ICAO Doc 4444 (PANS-ATM), §4.5.6.2 — supersonic flight clearances.
• ICAO Doc 7030 (Regional Supplementary Procedures) — supersonic vertical separation above FL450.
• ICAO Doc 10157 (PANS-MET), §8.2.3.2.1 — WAFS SIGWX chart ceiling FL600.
• FAA/NASA NARI ETM ConOps V1.0 (May 2020) and FAA HATM ConOps V2.0.
• SESAR 2020 ECHO ConOps (EUROCONTROL, H2020 grant 890417, 2020–2023).
• EASA HAO Roadmap (10 March 2023) and Contribution Agreement (11 November 2024).

What Higher Airspace Operations is#

Higher Airspace Operations (HAO) is the ICAO term for civil aviation activities conducted above the conventional upper limit of controlled airspace — operationally above approximately FL600 (60,000 ft / 18 km), where no systematic air traffic service currently exists. The altitude range in question spans from the ceiling of organised upper airspace (roughly FL600) to the lower boundary of space operations (variously placed between 80 and 100 km).

The term was given formal ICAO status in Assembly Resolution A41-9 (October 2022, Doc 10184). That resolution defines "New Entrants" as comprising HAO and UAS Traffic Management (UTM) operations, and directs ICAO to develop SARPs and guidance to enable New Entrant integration within a global, harmonised framework.

HAO is therefore not yet a deployed system. It is an active international programme to create a regulatory and operational framework where none currently exists. The FAA, EASA, EUROCONTROL, and ICAO are the principal institutional actors; industry bodies including the HAPS Alliance are engaged in parallel.

The altitude regime#

Conventional civil ATC service exists below approximately FL600. Between FL500 and FL600, conventional traffic density is low enough that the FAA HATM concept extends cooperative operations into this band. Above FL600, no ATC separation service exists; the HAO cooperative traffic management model applies.

The boundary is not yet enshrined in SARPs. Different working papers and ConOps documents use slightly different thresholds (FL550, FL600, FL650). FL600 is the most commonly cited reference level and is used throughout this folder.

Vehicle taxonomy#

HAO encompasses a wide range of vehicles with fundamentally different performance envelopes:

HAPS (High-Altitude Platform Stations) are the most operationally imminent category. They include solar-powered fixed-wing UAS (e.g. Airbus Zephyr, SoftBank HAPSMobile Sunglider, Joby Otos), aerostats, and solar-powered airships. They station-keep at FL600–FL800 for extended periods, potentially spanning multiple FIR boundaries, and are the primary driver of the current HAO regulatory programme.

HALE UAS differ from HAPS primarily in mission: they transit rather than station-keep, operate surveillance or relay payloads, and tend to traverse multiple national airspaces.

Civil supersonic aircraft re-enter the picture with a new generation of aircraft (e.g. Boom Overture, Spike Aerospace) targeting cruise altitudes of FL550–FL650. PANS-ATM §4.5.6.2 already carries ATC procedures for the transonic acceleration phase; the emerging supersonic category requires ATC coordination for the climb/descent corridor but self-separates during cruise.

Where HAO sits in the ICAO/ATM framework#

HAO occupies a gap in the ICAO framework structure:

• Below FL600: Annex 11 air traffic services, PANS-ATM procedures, regional supplementary procedures under Doc 7030.
• Above ~80 km: Space operations; Chicago Convention jurisdiction uncertain; ICAO A40-26 on Commercial Space Transport.
• FL600 to ~80 km: HAO — currently a gap, with only the general obligations of Annex 2 and Resolution A41-9 applying.

HAO therefore sits alongside UTM/U-space (low-level UAS) as one of the two "New Entrant" domains ICAO must regulate. Both share the cooperative traffic management model but at opposite altitude extremes. The design principles — operator accountability, shared operational intent, digital information exchange, cooperative deconfliction — are analogous.

Within the ASBU framework, HAO is not yet a named module. The closest existing threads are RPAS (RPAS integration into controlled airspace) and the emerging trajectory-based operations (TBO) concepts. If and when ICAO creates a formal HAO ASBU module, it would logically appear at Block 3 (2031+) horizon.

References#

• Doc 10184 (ICAO Assembly 41st Session Resolutions), Resolution A41-9 — formal definition of New Entrants as HAO plus UTM; ICAO direction to develop SARPs and guidance (authoritative source — not in local library).
• Annex 11 (Air Traffic Services), Chapter 2, §2.11.4 — Recommendation on upper airspace FIR/CTA delineation.
• Annex 2 (Rules of the Air), §3.3.1.4 and Appendix 3 — IFR requirement above FL200; modified cruising levels above FL410.
• FAA, Higher Airspace Traffic Management (HATM) ConOps V2.0 — FAA cooperative traffic management framework (authoritative source — not in local library).
• SESAR 2020 ECHO ConOps (EUROCONTROL-led, H2020 grant 890417, 2020–2023) — European concept for higher airspace operations (authoritative source — not in local library).

Building blocks of the HAO system#

Higher Airspace Operations is composed of four interdependent building blocks: the vehicle classes that operate in higher airspace, the airspace regime itself, the cooperative traffic management services that replace conventional ATC, and the transition corridor that connects higher airspace to conventional controlled airspace below.

1. Vehicle classes#

The following five vehicle classes define the HAO user community. Each has distinct performance, endurance, and airspace-interaction characteristics, requiring a flexible multi-class framework rather than a single separation standard.

• HAPS — heavier-than-air
  • Solar-powered fixed-wing UAS (e.g. Airbus Zephyr, SoftBank Sunglider)
  • Station-keeping at FL600–FL800 for days, weeks, or months
  • Near-zero cruise speed relative to the rotating earth
  • Missions: broadband connectivity, Earth observation, surveillance
  • Primary regulatory driver for the current ICAO/EASA HAO programme
• HAPS — lighter-than-air
  • Stratospheric aerostats, balloons, airships
  • FL600–FL1000; some wind-driven drift, some actively controlled
  • Long endurance; potential to span multiple FIRs simultaneously
  • Missions: persistent connectivity, scientific monitoring
• HALE UAS
  • High-Altitude Long-Endurance unmanned aircraft
  • FL550–FL700; transit missions crossing national airspaces
  • Typically faster than HAPS; climbs/descends through controlled airspace
  • Missions: surveillance, environmental sensing, relay
• Supersonic / hypersonic transients
  • Civil supersonic (FL550–FL700 cruise): next-generation passenger aircraft
  • Hypersonic (FL800–FL1200): research, potential future passenger service
  • PANS-ATM §4.5.6.2 already provides transonic clearance procedures
  • Key interaction point: climb/descent through conventional ATC
• Trans-atmospheric and suborbital vehicles
  • Steep ascent/descent profiles; brief HAO passage
  • Commercial space launch and return; experimental vehicles
  • Interact with HAO and ATC at the boundaries of their trajectory

2. The airspace regime#

The HAO airspace regime has three sub-layers that reflect the current and emerging regulatory framework:

• Conventional upper airspace (below FL600)
  • Defined Class A airspace in most regions
  • Full ATC separation service; RVSM above FL290
  • Conventional aircraft and initial transiting supersonic
  • Doc 7030 provides regional supplementary procedures
  • Annex 11 FIR and CTA structure applies
• Transition zone (FL500–FL600)
  • Conventional traffic density is low
  • FAA HATM ConOps V2.0 allows cooperative operations to extend down to approximately FL500 in low-density corridors
  • Both ATC-managed and cooperative operations may coexist
  • Transition rules govern entry to and exit from Cooperative Areas
• Higher airspace (above FL600)
  • No current systematic ATC service
  • Cooperative traffic management applies
  • Vehicle classes: HAPS, HALE UAS, supersonic transients, suborbital vehicles
  • HAO regulatory framework under development (ICAO A41-9 mandate; EASA NPA target September 2027)

3. Cooperative traffic management services#

Cooperative traffic management (CTM) is the defining service model for HAO above the conventional ATC floor. It comprises five service elements:

• Operational intent sharing
  • Operators broadcast 4D intent volumes: position, altitude, time window, and operational envelope
  • Analogous to SWIM-based flight information exchange but adapted for the non-ATS environment
  • Internet-based APIs (FAA HATM model) or SWIM service layer
  • Enables shared situational awareness across all HAO operators
• Cooperative deconfliction
  • Operators' automated systems compare intent volumes
  • Conflicts (overlapping volumes) are predicted and resolved through automated negotiation before they occur
  • Volume-based (intent envelopes), not position-and-minima-based
  • Human oversight at the operational level; automation handles the deconfliction cycle
• Cooperative Areas and Operating Procedures
  • Cooperative Areas (CAs): defined airspace volumes within which cooperative separation applies; FAA-authorised (HATM) or authority-approved (ECHO/EASA)
  • Cooperative Operating Procedures (COPs): operator-defined, authority-approved rules governing conduct inside a CA
  • Include: lost-link protocols, debris management, contingency procedures, coordination with ATC below the CA floor
• Information management layer
  • Digital service layer for intent data exchange
  • Spectrum and transponder code allocation for non-ADS-B compatible vehicles
  • Surveillance data fusion: space-based ADS-B where applicable, ground radar, ADS-C for high-altitude stations
  • Links to SWIM infrastructure for interoperability with conventional ATM information services
• ATC interface
  • At the transition boundary (approximately FL600), a handoff protocol connects cooperative operations above with ATC below
  • Analogous to the UAS/U-space ATC interface
  • Clearance for climb through controlled airspace remains an ATC responsibility (PANS-ATM §4.5.6.2 applies)
  • ATC retains separation responsibility for non-cooperative operations and contingency interventions

4. Transition corridor#

The transition corridor — the climb and descent profile through conventional controlled airspace — is the most critical interface point between HAO and existing ATM. It is where existing SARPs (PANS-ATM, regional supplementary procedures) already apply and where the regulatory gap is narrowest.

• Below the corridor: standard ATC Class A/B service
• Within the corridor: ATC clearance per PANS-ATM §4.5.6.2 (supersonic transonic phase provisions extended conceptually to all HAO vehicle types during climb/descent)
• Above the corridor: cooperative management takes over
• Coordination: the HAO operator files a transition notice with the relevant ACC; ATC provides a corridor clearance (lateral and vertical bounds, time window)
• Performance requirement: HAO operators must demonstrate navigation, communication, and lost-link procedures sufficient for the ATC authority to grant corridor access

The transition corridor concept is the HAO analogue of the U-space "Class C interface" for low-level UAS. Getting the corridor protocol right is the near-term regulatory priority: it can be addressed with targeted PANS-ATM amendments before a complete HAO framework is finalised.

References#

• Doc 4444 (PANS-ATM), Chapter 4, §4.5.6.2 — ATC clearances for supersonic transonic phase; basis for transition corridor procedure.
• Doc 7030 (Regional Supplementary Procedures), NAT §6.2.4.2 — 1,200 m (4,000 ft) VSM for supersonic aircraft at or above FL450.
• Annex 11 (Air Traffic Services), Chapter 2, §2.11.4 — upper airspace FIR/CTA delineation recommendation.
• FAA, HATM ConOps V2.0 — Cooperative Areas, COPs, cooperative deconfliction architecture (authoritative source — not in local library).
• SESAR 2020 ECHO ConOps (EUROCONTROL, H2020 grant 890417, 2020–2023) — European component taxonomy for higher airspace (authoritative source — not in local library).
• HAPS Alliance, Collaborative Traffic Management for the Stratosphere (CTMS) white paper — industry view on cooperative management framework (authoritative source — not in local library).

How to read this file#

HAO does not yet map to ASBU Blocks in the GANP sense. Instead, this file uses two complementary lenses: the vertical regime layers that define where different rules apply, and the programmatic maturity phases that describe how the HAO framework is being built globally. Both lenses are needed to understand the current state and trajectory of HAO development.

Vertical regime layers#

The airspace between the ground and space is divided into five layers for HAO planning purposes. Layers are defined by altitude, applicable rules, and the governing service model.

Maturity phases#

The HAO framework is progressing through three programmatic phases across ICAO, FAA, EASA, and industry.

Phase 1 — ConOps and demand analysis (2018–2026)#

The current phase. Multiple parallel initiatives producing the concepts of operations, demand analyses, and regulatory roadmaps that will seed the SARPs development phase.

Key milestones in this phase:

• ICAO Assembly A40-7 (2019) — predecessor New Entrants resolution; superseded by A41-9.
• FAA/NASA NARI ETM ConOps V1.0 (May 2020) — foundational cooperative traffic management concept for upper Class E (above FL600).
• ECHO project start (November 2020) — SESAR 2020 / H2020 European ConOps development; EUROCONTROL led.
• ICAO Assembly Resolution A41-9 (October 2022) — formal ICAO mandate; HAO defined as a New Entrant category; SARPs review directed.
• ECHO ConOps delivered (2023) — European demand analysis and operational concept; foundational for EASA regulatory work.
• EASA HAO Roadmap (10 March 2023) — European regulatory pathway delivered to the European Commission.
• FAA HATM ConOps V2.0 (2024) — updated FAA framework; Cooperative Areas and Cooperative Operating Procedures formalised.
• EASA Contribution Agreement (11 November 2024) — European Commission tasks EASA to prepare draft NPA by September 2027.
• ECHO 2 project start (2024) — SESAR 3 JU incremental validation under Horizon Europe (grant 101114697).
• ICAO 42nd Assembly WP/213 (2025) — strategic framework for HAO; proposal for ICAO HAO symposium and multidisciplinary working group.

Phase 2 — SARPs and regulatory framework (2026–2030)#

The anticipated next phase. Principal activities:

• ICAO HAO working group (proposed in WP/213); multidisciplinary; air navigation, certification, licensing, aviation law, space.
• ICAO HAO symposium — to build international consensus and establish working group mandate.
• EASA NPA for HAO regulatory framework (target September 2027).
• FAA rulemaking for HATM (timeline not published as at 2026).
• National regulatory actions in States operating significant HAPS or HALE UAS (Japan, US, UK, France, Germany).
• Revision of Annex 2 and Annex 11 to accommodate HAO (candidate for long-cycle amendment).
• Initial trial operations under national authorisations with agreed cooperative protocols.

Phase 3 — Initial operational implementation (2030+)#

The horizon phase. Indicators of Phase 3 readiness:

• ICAO SARPs amendment adopted covering at minimum the transition corridor and cooperative separation principles.
• At least one regional cooperative management framework operational (likely Europe, led by EASA-mandated rules).
• Commercial HAPS connectivity networks active (subject to ITU spectrum coordination alongside ICAO airspace rules).
• Routine supersonic passenger operations on North Atlantic and transpacific routes.
• ASBU module for HAO (HAPS/HAO thread) considered in GANP review cycle (GANP 8th edition, anticipated 2032).

Dependency chain#

The HAO framework cannot advance in isolation. Key dependencies:

• Annex 2 and Annex 11 amendment cycle — long lead time; must be initiated in Phase 2 to be adopted before Phase 3.
• ITU spectrum coordination — HAPS C2 links and payload frequencies require ITU approval alongside ICAO airspace rules.
• Vehicle certification — no ICAO category currently covers HAPS; EASA research project addresses this; FAA aircraft certification basis pending.
• UTM/U-space maturity — HAO cooperative model borrows from UTM; demonstrated UTM success strengthens the case for HAO adoption.
• SWIM and TBO infrastructure — the information exchange layer for HAO cooperative deconfliction is designed to interoperate with SWIM; TBO 4D intent sharing is a close analogue.

References#

• Doc 10184 (ICAO Assembly 41st Session Resolutions), Resolution A41-9 — ICAO mandate; HAO as New Entrant category (authoritative source — not in local library).
• Annex 11 (Air Traffic Services), Chapter 2, §2.11.4 — upper airspace FIR/CTA recommendation; Layer 1 governance basis.
• Doc 7030 (Regional Supplementary Procedures), NAT §6.2.4.2 — 1,200 m VSM at or above FL450; Layer 2 reference provision.
• FAA, HATM ConOps V2.0 — Phase 1/2 FAA framework; Cooperative Areas and COPs (authoritative source — not in local library).
• EASA HAO Roadmap (10 March 2023) and Contribution Agreement (11 November 2024) — European Phase 2 regulatory pathway (authoritative source — not in local library).
• SESAR 3 JU ECHO 2 project (Horizon Europe grant 101114697) — Phase 2 validation (authoritative source — not in local library).

A thread in the HAO context is a functional axis — a strand of development that must mature in parallel with the others for the overall HAO framework to work. Six threads run through the HAO programme. They are analogous to ASBU threads (feature areas grouping related operational improvements) but at the earlier research-and- concept stage rather than the deployment stage.

Thread 1 — Traffic management concept#

The core operational concept: how vehicles above FL600 are managed and kept safe from each other and from conventional traffic below.

The traffic management concept being developed across FAA, EASA, and ICAO converges on cooperative traffic management (CTM) as the primary model. CTM places separation responsibility on operators inside approved Cooperative Areas rather than on ATC. The key distinguishing features:

• Intent-volume deconfliction rather than position-minima separation. Operators declare 4D operational intent volumes; conflicts are resolved before they arise, not reactively.
• Automated deconfliction. Given the volume of potential interactions (especially when HAPS station-keeping intersects with transiting aircraft), human controller involvement for every pair interaction is not scalable. Automation handles routine deconfliction; human operators oversee exceptions.
• Operator accountability. Inside a CA, operators are responsible for their deconfliction conduct in accordance with the COPs. ATC retains authority at the boundaries.
• Scalability. The CTM model must scale from today's sparse operations (single HAPS trials) to a future with hundreds of HAPS, multiple supersonic routes, and routine suborbital flights.

The FAA HATM ConOps V2.0 and the ECHO ConOps are the most developed articulations of this concept. ICAO Assembly 42nd Session WP/213 proposed that an ICAO working group formalise the concept into candidate SARPs.

Thread 2 — Cooperative services and information exchange#

The information infrastructure that enables Thread 1 to function. Cooperative traffic management requires all participating operators to share operational intent data reliably, continuously, and in a mutually intelligible format.

Key elements of this thread:

• HAO information exchange service — analogous to SWIM but adapted for operations above FL600. Must handle diverse vehicle types, variable update rates, and long endurance missions.
• 4D operational intent volume — the data object that operators share: lateral extent, altitude block, time window, vehicle identity, capability statement, contact details.
• Service registry and access control — like SWIM service registries, the HAO information exchange needs a governance layer defining who can publish and who can consume intent data.
• Interoperability with SWIM — for vehicles that transition through controlled airspace, their intent data must be visible to both the HAO cooperative layer and conventional ATM information services. SWIM provides the downstream architecture.
• Surveillance data integration — space-based ADS-B (where vehicle ADS-B Out is fitted), ADS-C contracts for HAPS, ground-based radar below FL600. Not all HAO vehicles will carry 1090 ES transponders; the framework must accommodate alternative surveillance sources.

Thread 3 — Transition through controlled airspace#

The climb and descent corridor through Layers 1 and 2 (conventional upper airspace and the transition zone) is the most safety-critical interaction point between HAO and existing ATM.

Current normative basis:

• PANS-ATM §4.5.6.2 provides ATC clearance procedures for the transonic acceleration phase of supersonic flights, including the requirement to clear the transonic phase prior to departure where practicable, and to keep amendments to a minimum during the supersonic phase.
• Doc 7030 NAT §6.2.4.2 specifies 1,200 m (4,000 ft) vertical separation for supersonic aircraft at or above FL450.

These provisions are inadequate for the full range of HAO vehicles. Needed additions:

• Corridor clearance concept for non-supersonic HAO vehicles (HAPS, HALE UAS) climbing through Class A/B airspace.
• Performance requirements for corridor access: navigation accuracy, command and control link reliability, lost-link protocol, ATC voice/data communication capability.
• Separation standards within the transition zone (FL500–FL600) where cooperative and ATC-managed operations may coexist.
• Notification requirements: how far in advance must an HAO operator file a transition request, and to which unit.
• Contingency: what happens if a HAPS loses C2 link during the climb through controlled airspace.

This thread is the most tractable in the short term because it can be addressed with targeted PANS-ATM amendments building on existing §4.5.6.2 language before a complete HAO framework is in place.

Thread 4 — Vehicle certification and airworthiness#

No ICAO vehicle category currently covers the full range of HAO vehicles. The absence of a certification basis is a blocking enabler for commercialisation.

The certification challenge has three aspects:

Design standards. Annex 8 (Airworthiness) covers conventional aircraft categories. HAPS fall outside existing type definitions: they are not transport category aircraft, not general aviation, not remotely piloted aircraft systems (RPAS) as defined in existing ICAO provisions. A new category or a specific means of compliance is needed.

Operational approval. Even without a full type certificate, individual States can grant special authorisations for trial operations. Several HAPS operators have received such approvals (Airbus Zephyr in Arizona, SoftBank Sunglider in Japan). The HAO framework needs to harmonise these national authorisations into a common standard.

Environmental certification. HAPS and other HAO vehicles may affect the stratospheric environment (ozone layer interaction, radiative forcing of contrails at high altitude). ICAO CAEP has not yet defined emissions standards for HAO operations; this is an open item in the regulatory programme.

Thread 5 — Spectrum, command and control (C2), and communications#

HAO vehicles require reliable command and control links across inter-continental distances and long endurance missions. The spectrum and communications architecture is a major enabler.

• C2 link technology. HAPS and HALE UAS use satellite communications for beyond-visual-line-of-sight C2. Available technologies include Ku/Ka-band satcom, O3b/LEO constellations, and potentially direct RF links where ground coverage exists. Diversity and redundancy are safety-critical.
• Spectrum allocation. HAPS C2 frequencies require coordination with the ITU alongside ICAO airspace rules. The HAPS Alliance has engaged with ITU WRC cycles on HAPS spectrum. The aviation-specific C2 frequency band (5030–5091 MHz) was allocated for RPAS C2 and is candidate for HALE UAS; HAPS may require additional spectrum.
• ATC communication. Vehicles transiting through controlled airspace must meet ATC communication requirements (VHF voice or CPDLC as directed by the ATC authority). At HAO altitudes, conventional VHF does not provide coverage; HF or satcom data links are the alternative. The PANS-ATM requires ATC communication capability for the corridor clearance.
• Payload communications. HAPS are primarily connectivity platforms; their payload spectrum (broadband, LTE/5G, IoT) must be coordinated to avoid interference with aviation communication and navigation aids.

Thread 6 — International coordination and governance#

HAO is inherently cross-border. HAPS station-keeping positions may lie over multiple States simultaneously; supersonic routes cross dozens of FIRs; suborbital vehicles return to Earth anywhere in a re-entry corridor. No single State can regulate this unilaterally.

The governance requirements:

• ICAO framework. Assembly Resolution A41-9 tasked ICAO to develop the framework. The proposed working group (WP/213, 42nd Assembly) must include representatives from air navigation, certification, licensing, legal, and space domains.
• Bilateral and regional agreements. In the interim, States will need bilateral agreements or regional protocols (similar to the RVSM Letter of Agreement model) to manage cross-border HAPS operations. EASA will define a European framework through the regulatory programme (NPA target 2027).
• Liability framework. If a HAPS fails over a third State, the liability rules are unclear. Convention on International Civil Aviation Article 12 (rules of the air over high seas) and the space liability conventions both have partial applicability. A HAO-specific liability chapter in an ICAO instrument is needed.
• Civil-military coordination. HAO airspace overlaps with military operations at high altitude (reconnaissance, surveillance, test flights). Resolution A41-9 §3 requires that common use of airspace and facilities does not disproportionately affect regularity and efficiency of civil and military operations. Formal civil-military coordination protocols for HAO are needed.
• Space community interface. Assembly A41-9 §4 explicitly recognises the need for dialogue between States, New Entrants, aviation stakeholders, and the space community. The boundary between HAO and space is not yet legally defined. Coordination with national space agencies and UNOOSA is required.

Cross-thread dependencies#

• Thread 1 (TMC) depends on Thread 2 (information exchange) for its data layer and on Thread 3 (transition corridor) for its boundary protocol.
• Thread 2 depends on Thread 5 (C2/spectrum) for the communications infrastructure.
• Thread 4 (certification) depends on Thread 5 (C2) — no certification basis without demonstrated C2 reliability.
• Thread 6 (governance) provides the legal envelope within which Threads 1–5 operate; nothing can be mandated globally without the ICAO framework from Thread 6.

References#

• Doc 10184 (ICAO Assembly 41st Session Resolutions), Resolution A41-9 — mandate for Threads 1, 4, 6 (authoritative source — not in local library).
• Doc 4444 (PANS-ATM), Chapter 4, §4.5.6.2 — supersonic clearance procedures; Thread 3 normative basis.
• Doc 7030 (Regional Supplementary Procedures), NAT §6.2.4.2 — 1,200 m VSM at FL450+; Thread 3 SRP.
• Annex 11 (Air Traffic Services), Chapter 2, §2.11.4 — upper airspace FIR/CTA; Thread 6 governance basis.
• FAA, HATM ConOps V2.0 — Threads 1, 2, 3 FAA framework (authoritative source — not in local library).
• SESAR 2020 ECHO ConOps (EUROCONTROL, 2020–2023) — Threads 1, 2, 5 European concept (authoritative source — not in local library).
• HAPS Alliance, CTMS white paper — Thread 2 industry view; ITU spectrum coordination (authoritative source — not in local library).

HAO does not yet have an ASBU module catalogue. This file instead presents two worked examples that illustrate how the HAO threads and components interact in practice. The first traces the lifecycle of a HAPS mission through the transition corridor; the second describes the ETM cooperative deconfliction cycle for a volume conflict between two HAO operators.

Worked Example 1 — HAPS climb through controlled airspace#

This example traces the full climb-and-establish sequence for a solar-powered HAPS departing a ground station and transiting to its station-keeping position at FL700.

Scenario parameters#

• Vehicle: HAPS-type, max speed 80 kt, climb rate 500 ft/min
• Origin: ground station (airfield or dedicated launch site)
• Station-keeping position: FL700, within Cooperative Area CA-EUR-01 (hypothetical EASA-authorised CA over the eastern North Atlantic)
• Route: through Class D/C/A airspace (0 to FL245), then Class A upper airspace (FL245 to FL600), then HAO cooperative layer (FL600 to FL700)

Step 1 — Pre-mission notification#

The HAPS operator submits a transition request to the relevant Area Control Centre (ACC) at least 24 hours in advance. The request contains:

• Proposed climb corridor (lateral bounds, time window)
• Vehicle performance envelope (climb rate, speed, turn radius)
• C2 link details (primary satcom provider, backup frequency)
• Lost-link procedure (holding, controlled descent, emergency descent)
• Contact details for the remote pilot station

This notification is analogous to a special use airspace filing. No current PANS-ATM provision specifically addresses HAPS, but the ACC uses its existing authority under Annex 11 §2.11 to assess the request and issue a corridor clearance.

Step 2 — Transition clearance#

The ACC issues a corridor clearance specifying:

• Lateral block (typically a box centred on the climb trajectory)
• Vertical block (surface to FL600)
• Time window (estimated start plus buffer for slow climb rate)
• Communication requirement (satcom CPDLC or HF voice check-in)
• Separation from known traffic (the ACC deconflicts the HAPS corridor against filed flight plans for conventional traffic)

PANS-ATM §4.5.6.2.1 requires that, whenever practicable, supersonic aircraft be cleared for the transonic acceleration phase prior to departure. By analogy, best practice is for the HAPS corridor clearance to be issued before the vehicle becomes airborne.

Step 3 — Climb through conventional airspace#

The HAPS climbs through Class D, C, then A airspace. Due to the slow climb rate, transit of the Class A layer (FL245–FL600) may take 6–10 hours. During this phase:

• Standard ATC separation applies between the HAPS and conventional traffic.
• The HAPS is treated as a slow-climbing aircraft occupying the allocated corridor.
• The ACC periodically checks the HAPS against traffic; the corridor clearance provides the separation buffer.
• PANS-ATM contingency procedures apply: if the vehicle deviates outside the corridor, the ACC coordinates.

Doc 7030 NAT §6.2.4.2 (1,200 m VSM at FL450+ for supersonic aircraft) does not directly apply to HAPS, but its existence illustrates the principle that special separation standards already exist for non-standard vehicle interactions above conventional cruise.

Step 4 — HAO layer handoff#

As the HAPS passes approximately FL590–FL600:

• The ACC coordinates with the HAO cooperative management layer (or, in the near term, issues a procedural clearance to continue climb to the assigned station-keeping level).
• The vehicle operator registers the active mission in the HAO information exchange service for CA-EUR-01.
• The vehicle's 4D intent volume (FL650–FL750 station-keeping block for the mission duration) is published to all other CA-EUR-01 participants.
• ATC jurisdiction formally ends at the CA floor.

Step 5 — Station-keeping and cooperative management#

At FL700, the HAPS station-keeps. Its ongoing responsibilities:

• Maintain published intent volume; update if mission profile changes.
• Monitor the cooperative deconfliction service for conflicts with other CA participants.
• Execute any pre-agreed deconfliction manoeuvre (altitude adjustment, lateral offset) as required by COP.
• Maintain C2 link; execute lost-link procedure if link fails.

If a supersonic transient aircraft is filing a transit through the CA at FL680, the HAPS operator receives an automated deconfliction alert. The COP defines the precedence rule (e.g., transiting aircraft have priority over station-keeping operations within defined vertical margins). The HAPS climbs to FL720 for the transit window, then returns to FL700.

Step 6 — Descent and re-entry to controlled airspace#

On mission completion, the sequence reverses. The operator files a descent notification with the ACC. A descent corridor clearance is issued. ATC separates the HAPS from conventional traffic during descent through FL600 to the destination airfield.

Worked Example 2 — ETM cooperative deconfliction cycle#

This example describes the automated deconfliction cycle for a volume conflict in the FAA HATM framework, based on the HATM ConOps V2.0 model.

Scenario parameters#

• Cooperative Area: CA-USA-W01 (hypothetical FAA-authorised CA, western US, FL600–FL800)
• Operator A: HAPS station-keeping at FL700, 10 nm radius, 30-day mission (connectivity platform)
• Operator B: HALE UAS transiting FL650, estimated 4-hour overflight of CA-USA-W01 on a survey mission

Step 1 — Intent publication#

Both operators publish their 4D intent volumes to the CA's HAO information exchange service before entering the CA:

• Operator A: cylinder centred at 34.5N 118.0W, FL680–FL720, indefinite duration, updated every 15 minutes.
• Operator B: corridor 50 nm wide, FL640–FL660, entry at T+0 to T+4 hours, lateral route filed.

Step 2 — Conflict detection#

The cooperative deconfliction system detects that the transit corridor of Operator B intersects the intent volume of Operator A (overlapping altitude blocks) during a predicted 45-minute window.

The conflict is classified as a Schedule 2 conflict under the COPs (predicted overlap greater than 30 minutes, within defined proximity criteria).

Step 3 — Automated negotiation#

The system sends an automated conflict notification to both operators. Under the COPs, the transiting operator (B) has the obligation to adjust first for conflicts with established station-keeping operations.

Operator B's automated system proposes three resolution options:

• Option 1: descend to FL620–FL640 for the conflict window.
• Option 2: lateral deviation of 60 nm to the south.
• Option 3: delay entry to CA by 2 hours (shift time window).

Operator B selects Option 1. The adjusted intent volume is published. The deconfliction system confirms resolution. No human controller intervention is required.

Step 4 — Execution and monitoring#

Operator B descends to FL630 before entering the predicted conflict zone and maintains FL630 for the 45-minute window. During execution, both operators' automated systems monitor for deviations from the agreed intent.

If Operator A's HAPS drifts outside its intent volume (e.g. due to wind), an updated intent volume is published and the system re-checks for residual conflicts.

Step 5 — ATC interface (for reference)#

ATC at the adjacent ACC is aware of both operations but does not manage the deconfliction within the CA. The CA boundary is the handoff point. If either vehicle needs to transit back into controlled airspace during the conflict window, it requests a transition clearance from ATC, which then re-applies conventional separation logic.

Design principles illustrated by both examples#

Both worked examples demonstrate the same three HAO design principles drawn from the FAA HATM ConOps and ECHO ConOps:

1. Operator accountability inside CAs — separation responsibility resides with operators, not ATC.
2. Intent-before-encounter — deconfliction is pre-tactical, resolved before physical proximity, using shared intent data.
3. ATC as boundary manager — ATC manages the transition corridor and remains the backstop for non-cooperative emergencies, but is not the primary service provider inside the CA.

References#

• Doc 4444 (PANS-ATM), Chapter 4, §4.5.6.2 — ATC clearances for supersonic transonic phase; basis for transition corridor analogy in Example 1.
• Doc 7030 (Regional Supplementary Procedures), NAT §6.2.4.2 — 1,200 m VSM at FL450+ for supersonic aircraft; special separation precedent.
• Annex 11 (Air Traffic Services), Chapter 2, §2.11.4 — upper airspace FIR delineation; ATC authority context for corridor clearance.
• FAA, HATM ConOps V2.0 — Cooperative Areas, COPs, cooperative deconfliction cycle (Example 2 basis) (authoritative source — not in local library).
• SESAR 2020 ECHO ConOps (EUROCONTROL, 2020–2023) — European cooperative management model; Example 1 European context (authoritative source — not in local library).

What an enabler is in the HAO context#

An enabler is a prerequisite without which an HAO capability cannot be deployed safely. Because HAO is in the pre-regulatory phase, the enabler list is longer and less mature than for established ASBU capabilities. The enabling conditions range from fundamental (no certification basis exists for HAPS) to tractable near-term items (corridor clearance procedures can be added to PANS-ATM relatively quickly).

Enablers fall into six categories.

1. CNS infrastructure#

Communications#

• C2 links: HAPS and HALE UAS require beyond-visual-line-of-sight command and control links with demonstrated reliability sufficient for the certifying authority. Current options: Ku/Ka-band satcom, O3b/LEO constellations, L-band (Iridium). Redundancy and diversity are safety requirements; single-link operation is not acceptable for corridor transit through controlled airspace.
• ATC communication during transition: vehicles transiting through controlled airspace must communicate with ATC. VHF voice is the primary ATC medium but has limited range above FL350. HF voice (like oceanic operations), CPDLC over satcom (FANS-1/A model), or ATN B2 satcom extension are candidate means.
• Cooperative information exchange: the HAO digital information service (analogous to SWIM) must reach all CA participants with adequate latency. Terrestrial internet works for ground-based operator stations; the vehicle side requires satcom data link.

Navigation#

• Vehicle navigation: GNSS-based navigation using GPS and GNSS constellations is the primary means. Multi-constellation receivers improve availability. SBAS coverage diminishes above FL500 (the signal geometry degrades at high elevation). Aircraft-based augmentation (inertial/stellar hybrid) may be required for the highest HAPS operations.
• Corridor navigation: HAO vehicles in the transition corridor must demonstrate navigation accuracy adequate for ATC separation. Current RNAV or PBN specifications are designed for certified aircraft; equivalent performance requirements for HAPS remain to be defined.

Surveillance#

• ADS-B Out (1090 MHz): some HAO vehicles can carry 1090 ES transponders; this enables use of existing ADS-B ground stations and space-based ADS-B networks for surveillance. Not all HAO vehicle classes (LTA balloons, some aerostats) can carry this equipment.
• ADS-C: for persistent HAPS operations, periodic position reporting via ADS-C (satcom-based) provides surveillance when no ADS-B ground coverage exists. ADS-C is already the norm for oceanic surveillance of conventional aircraft.
• Space-based ADS-B: a growing network of low Earth orbit satellites receiving 1090 MHz transmissions provides coverage above FL400 in remote regions. This extends surveillance coverage into the transition zone and lower HAO layer.
• Non-ADS-B vehicles: aerostats, balloons, and vehicles unable to carry transponders require alternative surveillance (ground radar at close range, cooperative GPS position reporting via data link, space-based optical tracking). This is an open regulatory item.

2. Procedures#

• Corridor clearance procedure: a new PANS-ATM provision (or amendment to §4.5.6.2 and the surrounding sections) is needed to define the request-issue-revocation sequence for HAO vehicle transition corridor clearances.
• Lost-link protocol: a mandatory lost-link procedure for HAO vehicles in the transition corridor, specifying holding altitude, descent profile, or pre-planned recovery trajectory. ATC must know what the vehicle will do if C2 is lost while in controlled airspace.
• Contingency descent: if a HAPS must make an emergency descent through controlled airspace without a corridor clearance, a defined contingency procedure is needed so ATC can respond.
• COP publication: Cooperative Operating Procedures for each CA must be published in an aeronautical information product (AIP, SUP, or equivalent) so all potential participants know the rules.

3. Training and human performance#

• Remote pilot competency: no ICAO licensing standard covers remote pilots of HAPS or HALE UAS. Interim national authorisations define case-specific requirements. An ICAO standard (potentially via Annex 1 amendment or a new PANS chapter) is needed.
• Controller awareness: ATC controllers handling transition corridor clearances for HAO vehicles require awareness training covering vehicle performance (slow climb rates, inability to manoeuvre quickly, C2 link constraints) and the applicable emergency procedures.
• Operator authorisation: the approval body for operators seeking entry to a Cooperative Area must assess the operator's procedures, automation systems, and contingency plans. This is analogous to an ATM functional system approval under Annex 11.

4. Regulation and standards#

The key regulatory enablers are the items that must be in place before commercial HAO operations can be authorised at scale:

• ICAO SARPs: Assembly Resolution A41-9 directed ICAO to review and amend SARPs as necessary. Priority targets are Annex 2 (rules of the air), Annex 11 (ATS), and Annex 8 (airworthiness for a new HAPS/HALE category). Long cycle — amendments take several years to adopt.
• EASA regulatory framework: the NPA due by September 2027 will define the European rules for HAO vehicle certification and operations within the EU. Once adopted, it becomes the most developed regional standard globally.
• FAA rulemaking: the FAA HATM ConOps V2.0 is the operational basis; FAA must translate it into rulemaking to give operators legal certainty.
• Airspace designation: national authorities must formally designate HAO corridors and Cooperative Areas in their aeronautical information publications, specifying the floor, ceiling, and applicable COPs.

5. Institutional arrangements#

• ICAO HAO working group: the proposed multidisciplinary group (WP/213, 42nd Assembly) to develop the global framework. Without a formal ICAO body, the FAA and EASA frameworks will diverge.
• Bilateral and regional agreements: in the absence of global SARPs, cross-border operations require bilateral letters of agreement or regional protocols between the relevant States and ANSPs. The RVSM Letter of Agreement model (adopted for 300 m VSM before global SARPs existed) is a precedent.
• Civil-military coordination bodies: HAO operations overlap with high-altitude military activity. Existing civil-military ATM coordination bodies (EUROCONTROL CMC, FAA AF ASPM) need to extend their scope to HAO.
• ITU coordination: HAPS frequency assignments require coordination through the ITU World Radiocommunication Conference (WRC) cycle. The HAPS Alliance has engaged WRC processes. ICAO and ITU must coordinate to ensure aviation C2 spectrum and payload spectrum do not conflict with aviation navigation and communication bands.

6. Environmental certification#

• Emissions: HAO vehicles operating at stratospheric altitudes interact with the ozone layer and have different climate forcing than conventional tropospheric aircraft. ICAO CAEP has not yet defined emissions standards for HAO. Environmental certification criteria are a blocking enabler for HAPS proliferation.
• Noise: HAPS and HALE UAS noise at ground level is low, but trans-atmospheric vehicles may generate sonic booms. Annex 16 Volume I addresses subsonic aircraft; no equivalent standard exists for supersonic HAO transients or trans-atmospheric vehicles.
• Debris: HAPS failure at altitude can produce debris falling over populated areas. The certification basis must define design standards for controlled descent or debris containment, analogous to the JARUS UAS Risk Assessment categories at low altitude.

References#

• Doc 10184 (ICAO Assembly 41st Session Resolutions), Resolution A41-9 — mandate for SARPs review and guidance development (authoritative source — not in local library).
• Annex 11 (Air Traffic Services), Chapter 2, §2.11.4 — institutional basis for upper airspace ATS; FIR/CTA delineation.
• Doc 4444 (PANS-ATM), Chapter 4, §4.5.6.2 — supersonic clearance procedures; procedural basis for corridor clearance concept.
• Doc 7030 (Regional Supplementary Procedures), NAT §6.2.4.2 — 1,200 m VSM at FL450+; SRP procedural enabler.
• FAA, HATM ConOps V2.0 — enabler list for US cooperative framework; transition procedures (authoritative source — not in local library).
• EASA Contribution Agreement (11 November 2024) — mandate for EASA NPA by September 2027; regulatory enabler pathway (authoritative source — not in local library).
• HAPS Alliance, CTMS white paper — spectrum and C2 enablers from industry perspective (authoritative source — not in local library).

Performance framework for HAO#

HAO does not yet have an adopted ICAO performance framework. The Key Performance Areas (KPAs) from Doc 9854 / Doc 9883 (the ASBU performance model) apply by analogy, but several need reinterpretation for the HAO context. Two additional KPAs — Access and Environmental protection — are particularly prominent in HAO given the vehicle diversity and the stratospheric environment.

This file adapts the eleven ASBU KPAs to the HAO domain, proposes a numeric contribution matrix across the three maturity phases (ConOps, SARPs/framework, operational), and lists the principal KPIs that a future HAO performance monitoring scheme would use.

HAO-adapted KPAs#

KPA contribution matrix by maturity phase#

The matrix scores each KPA by its principal benefit horizon across the three HAO maturity phases (1 = some benefit, 2 = clear benefit, 3 = primary driver). Phase 1 = ConOps; Phase 2 = SARPs/framework; Phase 3 = operational implementation.

Performance objectives#

Safety#

• PO-HAO-S1: Ensure separation between HAO vehicles and conventional aircraft in the transition corridor. Target: zero ATC separation minima infringements during corridor transit.
• PO-HAO-S2: Ensure cooperative deconfliction in Cooperative Areas resolves all predicted conflicts before vehicle proximity falls below the agreed separation standard. Target: 100% resolution rate before T-minus contingency threshold.
• PO-HAO-S3: Define and exercise lost-link procedures for HAPS in transition corridor. Target: recovery within defined time and altitude parameters in 100% of simulated lost-link events.

Capacity#

• PO-HAO-C1: Define maximum concurrent vehicle count per Cooperative Area consistent with safe cooperative deconfliction performance. Target: to be established per CA based on deconfliction system capacity analysis.
• PO-HAO-C2: Transition corridor throughput. Target: not to be a limiting factor for HAPS mission start rates; acceptable corridor occupancy time per vehicle.

Interoperability#

• PO-HAO-I1: Common intent volume data format across all CAs (FAA, EASA, and other national frameworks). Target: at least one bilateral CA interface operational by end of Phase 2.
• PO-HAO-I2: Mutual recognition of operator authorisations between at least US and European frameworks. Target: framework agreement signed by Phase 3 entry.

Environmental#

• PO-HAO-E1: Characterise and monitor the stratospheric impact of HAPS operations. Target: CAEP study group established and initial assessment completed within 5 years of first commercial HAPS operations.
• PO-HAO-E2: Define acceptable sonic boom exposure limits for civil supersonic operations (analogous to noise certification thresholds). Target: CAEP standard adopted before supersonic aircraft service entry.

KPIs for HAO monitoring#

The following KPI families would populate a future HAO performance monitoring report, analogous to the EUROCONTROL PRB annual review for conventional ATM.

Safety KPIs#

• Corridor conflict rate: number of unresolved separation events per 1,000 corridor transit operations.
• Cooperative deconfliction success rate: percentage of detected conflicts resolved by automated negotiation before contingency threshold.
• Lost-link events per 1,000 flight hours: rate of C2 link interruptions affecting cooperative management.
• ATC-issued collision alerts involving HAO vehicles.

Capacity KPIs#

• Active HAPS per Cooperative Area per day.
• Corridor clearance lead time: mean time from request to issuance.
• Corridor transit duration per vehicle (impacts area occupancy time available to other vehicles).

Interoperability KPIs#

• Common data format coverage: percentage of operational Cooperative Areas using agreed intent volume data format.
• Cross-border intent data exchange operational: binary (yes/no) per bilateral pair.

Environmental KPIs#

• HAPS fleet altitude-hours in the ozone-sensitive layer (18–25 km): reported annually as input to CAEP environmental assessment.
• Sonic boom complaints per supersonic flight (track-based).

Access and equity KPIs#

• Number of States with authorised Cooperative Areas.
• Operator approval lead time: time from application to first authorisation.
• Spectrum interference events per 1,000 HAPS flight hours.

References#

• Doc 9854 (Global ATM Operational Concept), Chapter 2 — eleven KPAs; ATM performance framework basis.
• Doc 9883 (Manual on Global Performance of the Air Navigation System) — KPA definitions and performance monitoring framework.
• Doc 10184 (ICAO Assembly 41st Session Resolutions), Resolution A41-9 — safety, regularity, and efficiency as the goals for New Entrant integration (authoritative source — not in local library).
• FAA, HATM ConOps V2.0 — operational intent and deconfliction success as safety metrics (authoritative source — not in local library).
• SESAR 2020 ECHO ConOps (EUROCONTROL, 2020–2023) — performance objectives for European HAO (authoritative source — not in local library).

Reading this file#

The timeline traces the development of the HAO concept from early high-altitude flight milestones through the emergence of the modern HAPS industry, the first regulatory frameworks, and the ICAO mandate. The auto-viz plugin renders a Timeline from the Year column.

Key milestones#

Contextual notes#

The timeline shows two parallel tracks: the HAPS connectivity industry moving toward commercialisation through national authorisations, and the institutional track (FAA, EASA, ICAO) developing the regulatory framework. The risk is that the commercial track outpaces the regulatory track, creating a patchwork of incompatible national rules before global harmonisation is achieved. Assembly Resolution A41-9 and the ICAO 42nd Assembly WP/213 are the institutional responses to this risk.

The supersonic re-entry track (Boom Overture, Spike Aerospace) is approximately 5–10 years behind the HAPS track, giving more time for regulatory development, but the sonic boom and airspace integration challenges are distinct from the HAPS cooperative management challenge.

References#

• Doc 10184 (ICAO Assembly 41st Session Resolutions), Resolution A41-9 (October 2022) — ICAO New Entrants mandate (authoritative source — not in local library).
• Annex 11 (Air Traffic Services), Amendment 22 history table — supersonic provisions added 1975; basis for §3.7 ATC of supersonic aircraft.
• FAA/NASA NARI, ETM ConOps V1.0 (May 2020) — foundational FAA cooperative traffic management concept (authoritative source — not in local library).
• SESAR 2020 ECHO ConOps (EUROCONTROL, H2020 grant 890417, completed January 2023) (authoritative source — not in local library).
• EASA HAO Roadmap (10 March 2023) and Contribution Agreement (11 November 2024) (authoritative source — not in local library).
• FAA, HATM ConOps V2.0 (2024) (authoritative source — not in local library).

This file consolidates all ICAO and authoritative external references used across the HAO topic folder. References are grouped by source type.

ICAO instruments#

• Doc 10184 (ICAO Assembly 41st Session Resolutions), Resolution A41-9, §1–5 — New Entrants: formal definition of HAO plus UTM as New Entrant categories; direction to review SARPs; call on States to arrange regulations; ICAO role as international forum; supersedes A40-7 (authoritative source — not in local library).
• Annex 2 (Rules of the Air), §3.3.1.4 — IFR requirement for flights above FL200; basis for HAO vehicle IFR obligations during transition.
• Annex 2 (Rules of the Air), §3.6.2.1 and Appendix 3 — modified table of cruising levels for flights above FL410 by regional agreement; normative basis for modified cruising structure at HAO altitudes.
• Annex 11 (Air Traffic Services), Chapter 2, §2.11.4 — Recommendation on delineation of FIR or control area covering upper airspace to limit transit through multiple lower FIRs; foundational upper airspace governance provision.
• Doc 4444 (PANS-ATM), Chapter 4, §4.5.6.2 — ATC clearances for supersonic flight: transonic acceleration phase, keeping amendments to a minimum during supersonic phase, deceleration/descent; most directly applicable current PANS to HAO transition corridor.
• Doc 7030 (Regional Supplementary Procedures), NAT region §6.2.4.2 — at or above FL450, 1,200 m (4,000 ft) vertical separation minimum between supersonic aircraft; live SRP for the emerging altitude band.
• Doc 10157 (PANS-MET), Chapter 8, §8.2.3.2.1 — minimum charts for flights above FL100 include WAFS SIGWX FL100–FL600; the FL600 ceiling implicitly defines the top of current MET service.
• Doc 9854 (Global ATM Operational Concept), Chapter 2 — eleven KPAs; flexible use of all airspace; basis for HAO performance framework.
• Doc 9883 (Manual on Global Performance of the Air Navigation System) — KPA definitions and global performance monitoring basis.

FAA instruments#

• FAA / NASA NARI, Upper Class E Traffic Management (ETM) Concept of Operations V1.0 (May 2020) — foundational cooperative traffic management concept for airspace above FL600; cooperative vs ATC-managed operations; vehicle types; three operating principles (authoritative source — not in local library).
• FAA, Higher Airspace Traffic Management (HATM) ConOps V2.0 (2024) — updated framework; Cooperative Areas (CAs); Cooperative Operating Procedures (COPs); automated deconfliction via shared operational intent volumes (authoritative source — not in local library).
• FAA Fact Sheet: Upper Class E Airspace Traffic Management (ETM) (July 2022) — public summary of ETM concept; definition of upper Class E above FL600 (authoritative source — not in local library).

European instruments#

• SESAR 2020 / H2020 ECHO project (grant 890417), ConOps for Higher Airspace Operations (delivered January 2023) — EUROCONTROL-led; demand analysis; operational concept; vehicle taxonomy; CNS requirements; information management; foundational for EASA regulatory work (authoritative source — not in local library).
• SESAR 3 JU ECHO 2 project (Horizon Europe grant 101114697, from November 2024) — incremental validation of ECHO ConOps under Digital European Sky programme (authoritative source — not in local library).
• EASA, Proposal for a Roadmap on Higher Airspace Operations (HAO) (10 March 2023) — European regulatory pathway; certification, operations, environmental scope; delivered to European Commission (authoritative source — not in local library).
• European Commission — EASA Contribution Agreement (11 November 2024) — Commission mandate to EASA to prepare draft regulatory framework (NPA) for HAO by September 2027; proportionate certification requirements (authoritative source — not in local library).

ICAO Assembly working papers#

• ICAO 41st Assembly WP/085 (2022) — working paper on higher airspace operations; background and scope; precursor to Resolution A41-9 (authoritative source — not in local library).
• ICAO 42nd Assembly WP/213 (2025) — strategic framework for HAO; proposal for ICAO HAO symposium and multidisciplinary working group spanning air navigation, certification, licensing, aviation law, and space (authoritative source — not in local library).

Industry and research#

• HAPS Alliance, Collaborative Traffic Management for the Stratosphere (CTMS) white paper — industry vision for globally harmonised, cross-border cooperative management; ITU spectrum coordination; informed by UTM principles (authoritative source — not in local library).
• NASA Technical Memorandum TM-20220015612, Cooperative Separation in Upper Class E Airspace (2022) — NASA research on cooperative separation strategies and solutions for ETM (authoritative source — not in local library).

External URLs#

• https://www.icao.int/sites/default/files/Meetings/a41/Documents/WP/wp_085_en.pdf - ICAO 41st Assembly WP/085 — HAO working paper
• https://www.icao.int/sites/default/files/Meetings/a42/Documents/WP/wp_213_en.pdf - ICAO 42nd Assembly WP/213 — HAO strategic framework
• https://nari.arc.nasa.gov/sites/default/files/attachments/ETM_ConOps_V1.0.pdf - NASA NARI ETM ConOps V1.0 (May 2020)
• https://www.faa.gov/uas/advanced_operations/higher_airspace/HATM_ConOps_v2.pdf - FAA HATM ConOps V2.0
• https://www.faa.gov/uas/advanced_operations/hatm - FAA HATM programme page
• https://www.easa.europa.eu/en/downloads/137741/en - EASA HAO Roadmap (March 2023)
• https://www.easa.europa.eu/en/the-agency/faqs/higher-airspace-operations-hao - EASA HAO FAQ
• https://www.easa.europa.eu/en/research-projects/research-project-regulatory-framework-higher-airspace-operations-hao - EASA HAO regulatory framework research project
• https://www.eurocontrol.int/project/european-concept-higher-airspace-operation - EUROCONTROL ECHO project page
• https://www.sesarju.eu/projects/echo - SESAR JU ECHO project
• https://higherairspace.eu/ - ECHO 2 project website (SESAR 3 JU / Horizon Europe)
• https://hapsalliance.org/ - HAPS Alliance
• https://cordis.europa.eu/project/id/890417 - EU CORDIS ECHO project record (H2020 grant 890417)
• https://ntrs.nasa.gov/api/citations/20220015612/downloads/NASA-TM-20220015612.pdf - NASA TM cooperative separation in upper Class E airspace