Detailed working notes on the ICAO Circular publication class. This folder expands the summary in topics/icao_circulars.md into per-aspect files so each can be read on its own.

Unlike most other folders in this workspace (which describe an operational concept or an ATM capability), this folder describes a document class — the format, status, governance, and historical catalogue of ICAO Circulars.

Files in this folder#

• overview.md — what an ICAO Circular is, where it sits in the ICAO publication hierarchy, and how it relates to Annexes, PANS, and Doc-series manuals.
• components.md — typical structure of a Circular, its numbering convention, and the issuing authorities (Air Navigation Commission, Council, Secretariat).
• blocks.md — adapted: the subject domains that Circulars cover (safety, operational/ATM, environment, economics, statistics, facilitation, security, training).
• threads.md — adapted: the typical use-cases in which Circulars are issued (case studies, statistical reviews, special situations, transitional guidance, panel output).
• modules.md — anatomy of a single Circular: title block, purpose, scope, audience, status, content body, references.
• enablers.md — the ICAO bodies that originate Circulars: Air Navigation Commission panels, study groups, working groups, and Secretariat bureaux.
• performance_objectives.md — how Circulars support the wider performance and safety frameworks through information dissemination, even though they carry no SARP weight themselves.
• timeline.md — examples of notable Circulars across the running series, from the early single-digit numbers to the current mid-300s (Cir 113, 120, 295, 314, 327, 328, 330, 344, 351 and others).
• references.md — ICAO Publications portal, ICAO Store catalogue, SKYbrary mirrors, and a list of representative Circulars by number.

Reading order#

Start with overview.md to fix the publication-hierarchy context, then components.md for format and numbering. Read blocks.md and threads.md together to understand subject coverage and use-case mix. Use modules.md for the anatomy of a single document. Use enablers.md to see who originates Circulars, performance_objectives.md for the role they play in implementation, timeline.md for the historical catalogue, and references.md for citations.

Source basis#

Content is grounded in:

• ICAO publications policy as expressed across the Annexes, PANS, and Doc-series.
• Cross-references to specific Circulars from inside the local ICAO Markdown library (Annex 11, Doc 9587, Doc 9626, Doc 9379, Doc 8335, PANS-TRG Doc 9868, and others).
• The ICAO Publications portal: https://www.icao.int/publications
• The ICAO Store catalogue: https://store.icao.int
• SKYbrary bookshelf mirror: https://skybrary.aero/bookshelf

What an ICAO Circular is#

An ICAO Circular is a class of ICAO publication used to disseminate specialized information of interest to Contracting States and the wider aviation community. A Circular packages study material, statistical compilations, panel output, transitional guidance, or special-situation analysis that ICAO has decided is worth publishing under its own imprimatur but that is not intended to carry the formal weight of a Standard, Recommended Practice, or Procedure.

Circulars are part of the regular ICAO output stream alongside Annexes, PANS, Doc-series manuals, and Regional Supplementary Procedures. They are reviewed before publication, carry an ICAO publication number, and are sold through the ICAO Store and listed in the ICAO Publications catalogue.

Status — informational, not SARP#

A Circular is not a Standard. The defining points are:

• No obligation under Article 38 of the Chicago Convention. States do not file differences against a Circular. Implementation is voluntary.
• No PANS status. A Circular does not prescribe operational procedures the way Doc 4444 (PANS-ATM), Doc 8168 (PANS-OPS), or Doc 10066 (PANS-AIM) do.
• No manual status. A Circular is typically narrower in scope than a Doc-series manual; manuals consolidate mature guidance, Circulars often present interim or specialized material.
• Authoritative within its domain. Despite the lower formal weight, Circulars are produced by ICAO panels and Secretariat, reviewed by the Air Navigation Commission where appropriate, and routinely cited in CAA advisory circulars, ANSP procedures, and training syllabi.

A useful mental rule: a Circular tells you what ICAO has studied or has observed; an Annex tells you what States shall or should do; a PANS or manual tells you how.

Where Circulars sit in the publication hierarchy#

The ICAO publication hierarchy, from highest to lowest formal weight:

1. Annexes to the Chicago Convention — Standards (binding subject to filed differences) and Recommended Practices.
2. Procedures for Air Navigation Services (PANS) — operational procedures elaborating SARPs (Doc 4444, Doc 8168, Doc 9868, Doc 8400, Doc 10066, Doc 10157).
3. Regional Supplementary Procedures (SUPPS) — Doc 7030.
4. ICAO Doc-series manuals and guidance — consolidated technical manuals (e.g. Doc 9613 PBN Manual, Doc 9328 RVR Manual, Doc 9859 Safety Management Manual).
5. ICAO Circulars — specialized information, studies, interim guidance, statistical reviews.

A given subject can travel up this hierarchy as it matures. Circular 113 supplied the original RVR material and was later consolidated into Doc 9328 (the RVR Manual). Circular 295 (early PBN guidance) was substantially absorbed into Doc 9613 (PBN Manual). Circular 328 (UAS) seeded the work that produced Doc 10019 (RPAS Manual) and amendments to Annex 2 and Annex 7.

Relationship to Annexes and PANS#

Circulars routinely work alongside SARPs in three ways:

• Underpinning study. An Annex provision references a Circular for the methodology behind a numerical value. Annex 11 references Circular 120 for the parallel-track separation methodology (§3.1 and Attachment material, see Annex 11 (Air Traffic Services), Attachment A — parallel-track derivation).
• Implementation guidance. A PANS or manual cites a Circular for human-factors or training context. PANS-TRG (Doc 9868) cites Circular 314 for the Threat and Error Management framework used in ATCO training (§ Part II, Section 1, Chapter 6 and the document's glossary).
• Pre-SARP exploration. A Circular publishes the exploratory work before the corresponding Annex amendment is mature (the Cir 328 → Annex 2 / Annex 7 / Doc 10019 trajectory for UAS is the canonical example).

Why Circulars exist#

Circulars give ICAO a way to publish material that would not fit the deliberation cycle of an Annex amendment but that the community needs soon. Specifically:

• Speed. A Circular can be issued within months of panel endorsement; an Annex amendment cycle is multi-year.
• Specificity. Circulars can cover a single aircraft type (Cir 327 on the A380 wake), a single event class (Cir 344 on fume events), a single procedural topic (Cir 120 on parallel tracks), or a single audit programme (Cir 335 on USOAP-CMA).
• Statistical and economic reporting. Many Circulars in the early numbering are pure statistical compilations (traffic, fleet, fuel use) that serve as inputs to economic and policy work.
• Transitional guidance. When a SARP regime is changing, a Circular bridges the gap (the AIS-to-AIM transitional material that preceded Annex 15 Amendment 40 and Doc 10066).

How Circulars are used in this workspace#

Other topic files in this workspace cite Circulars where they contain the source material for an operational concept (e.g. ATFM, UAS, FUA, parallel-track separation). The topics/icao_circulars.md page provides the consolidated public-facing summary; this folder is the detailed reference for the document class itself.

A Circular is not just a topic; it is a recognisable publication type with a defined structure, numbering convention, and issuing authority. This file describes those components.

1. The numbering system#

Circulars are issued in a single running sequential series, prefixed "Cir" (sometimes spelled out as "Circular" in cross-references). The number is followed by an "AN/" suffix that gives the Air Navigation Bureau working number under which the document was prepared.

Format:    Cir <NNN> AN/<MMM>
Examples:  Cir 295 AN/175
           Cir 314 AN/178
           Cir 328 AN/190
           Cir 330 AN/189
           Cir 351                 (Eleventh Edition; AN suffix may be dropped)

Key properties of the numbering:

• Single running series. All Circulars share one number space irrespective of subject domain. Cir 269 (codesharing economics) and Cir 270 (a separate operational topic) sit next to each other in the catalogue.
• The number is not the subject. Cir 314 is human factors; Cir 328 is UAS; Cir 330 is civil-military ATM. Subject is given by the title.
• The AN/ working number is internal bookkeeping. It identifies the Air Navigation Bureau working file. Two consecutive Circulars need not have consecutive AN/ numbers.
• Sequential issuance. Numbering starts in the early 1940s with Cir 1 and runs through the current mid-300s.
• Single-edition unless explicitly revised. A Circular is not amended in the way an Annex is. When material needs revision the Circular is either superseded by a new Circular at a higher number, absorbed into a manual, or re-issued as a numbered new edition (e.g. Cir 351 — En-route Navigation Strategy, Eleventh Edition).
• Withdrawal rather than re-issue. When the underlying material matures into a manual or an Annex provision, the Circular is normally withdrawn from sale.

2. The title block#

The first page of a Circular carries:

• The full title — usually descriptive and self-contained, e.g. "Threat and Error Management (TEM) in Air Traffic Control" or "Civil/Military Cooperation in Air Traffic Management".
• The Circular number and AN/ working number.
• The publication date (year).
• The ICAO logo and standard ICAO publication branding.
• An ISBN.
• A formal statement that the document is a Circular, with the standard caveat: "approved by the Secretary General and published under his authority" (or equivalent depending on issuing path).

3. Issuing authority#

Three internal paths produce Circulars; the title block usually makes the path clear.

Air Navigation Commission (ANC) panels#

Most operational and technical Circulars originate in an Air Navigation Commission panel or study group. Examples:

• Cir 314 (TEM in ATC) — origin in the Operations Panel / human-factors work supporting ATCO training.
• Cir 328 (UAS) — work of what later became the Remotely Piloted Aircraft Systems Panel (RPASP).
• Cir 330 (Civil/Military Cooperation) — Civil/Military Cooperation Working Group reporting to the ANC.
• Cir 120 (parallel tracks) — Separation and Airspace Safety Panel (SASP) and predecessor groups.

ICAO Council#

A small number of Circulars are issued under Council direction — typically those carrying an economic, policy, or facilitation message that cuts across bureaux. Doc 9587 (economic regulation policy) and Doc 9626 (regulation of international air transport) are not Circulars but Council-policy Docs; the parallel Council-driven Circulars cover audits, statistics, and economic guidance.

Secretariat (Secretary General)#

Statistical, financial, and administrative Circulars are issued by the Secretariat under the Secretary General's authority, often through the Air Transport Bureau (ATB) or the Bureau of Administration and Services. The Secretariat path also publishes Circulars that compile expert-meeting outcomes or transitional guidance for States.

4. Internal structure of a Circular#

The body of a typical Circular contains:

1. Foreword — purpose of the Circular, status, intended audience.
2. Table of contents.
3. Glossary / definitions specific to the subject.
4. Main chapters — the technical content.
5. Appendices — supporting tables, methodologies, sample forms, reporting templates.
6. References — Annexes, PANS, manuals, and external standards.

Length varies widely. Statistical Circulars can be tens of pages of tables. A subject Circular like Cir 328 (UAS) or Cir 330 (Civil/Military Cooperation) runs to roughly 60–120 pages with multiple appendices.

5. Languages#

Like other ICAO publications, Circulars are produced in the six ICAO official languages — English, French, Spanish, Russian, Arabic, Chinese — though the publication date in each language can stagger by several months.

6. Distinguishing a Circular from neighbouring publication types#

The simplest test: if it has SARPs, it is an Annex. If it tells you how to do something procedurally, it is a PANS. If it consolidates mature guidance for an audience, it is a Doc-manual. If it is a study, report, or panel-issued specialized material, it is a Circular.

This file is the Circulars equivalent of the asbu Blocks view: it groups Circulars by subject domain rather than by chronology or operational thread. The Circular numbering is a single running series (see components.md); subject domain has to be inferred from each Circular's title and content.

The domains below reflect the practical clusters that recur across the catalogue. A given Circular usually fits one domain, occasionally two.

Domain 1 — Safety and Human Performance#

Circulars that publish safety methodology, human-factors frameworks, incident-class guidance, and safety-oversight material.

Representative Circulars:

• Cir 314 — Threat and Error Management (TEM) in Air Traffic Control. The reference framework for TEM in ATCO operations, cited from PANS-TRG (Doc 9868) Part II, Section 1, Chapter 6.
• Cir 335 — Manual on the USOAP Continuous Monitoring Approach (USOAP-CMA). Audit-protocol material covering State safety oversight including ANS provision (ANS PQs).
• Cir 344 — Guidelines on Education, Training and Reporting Practices related to Fume Events. Cabin-air-quality safety reference cited from occurrence-handling and CRM training material.

Domain character: human-factors, training, oversight, occurrence classification. Heavy reliance on Annex 1 (Personnel Licensing), Annex 13 (Investigation), and Annex 19 (SMS).

Domain 2 — Operational / ATM#

Circulars that address air-traffic-services concepts, separation methodologies, airspace organisation, and flow management.

Representative Circulars:

• Cir 120 — Methodology for the Derivation of Separation Minima Applied to the Spacing Between Parallel Tracks. The mathematical basis behind parallel-route lateral separation; referenced from Annex 11 Attachment material and Doc 9426 (ATS Planning Manual).
• Cir 295 (in the air-navigation context) — Guidance on the Implementation of Article 83 bis — operational/legal context for cross-border operating responsibilities (cited from Doc 8335 and Doc 9379).
• Cir 327 — Wake Turbulence Aspects of Airbus A380-800. Issued ahead of Doc 4444 amendments and feeding into RECAT-ICAO.
• Cir 330 — Civil/Military Cooperation in Air Traffic Management. Flexible Use of Airspace (FUA), cross-domain coordination, State aircraft operations, ATM security.

Domain character: separation, airspace, flow, civil/military coordination. Anchored in Annex 11 (ATS) and Doc 4444 (PANS-ATM).

Domain 3 — Communications, Navigation, Surveillance (CNS)#

Circulars on CNS systems and their operational implications.

Representative Circulars:

• Cir 113 — Visibility / Runway Visual Range. Original RVR material; matured into Doc 9328 (RVR Manual).
• Cir 295 (PBN context) — Guidelines for the Implementation of GNSS- aided RNAV. Early PBN guidance; substantially absorbed into Doc 9613 (PBN Manual).
• Cir 351 — En-route Navigation Strategy (Eleventh Edition). Strategic PBN, RNP, and conventional NAVAID rationalisation guidance for States and regions.

Note that "Cir 295" appears twice in different contexts in older and newer references; always check the full title to disambiguate. Doc 8335 and Doc 9379 cite the Article 83 bis Cir 295; the PBN community references the GNSS-RNAV implementation Cir 295.

Domain character: CNS infrastructure, navigation strategy, surveillance technology. Anchored in Annex 10 (Aeronautical Telecommunications) and Doc 9613 (PBN).

Domain 4 — Environment#

Circulars on aviation environmental performance: emissions, noise, operational improvements with environmental benefit.

Representative Circulars:

• Various Circulars in the Cir 200-series on aircraft engine emissions, fuel-burn methodology, and the basis of Annex 16 Volumes I–IV.
• Environmental review compilations issued periodically as Circulars when between ICAO Environmental Reports (which are themselves not Circulars but stand-alone publications).

Domain character: emissions inventories, noise, operational environmental benefit. Anchored in Annex 16 (Environmental Protection).

Domain 5 — Economics and Statistics#

Numerically the largest domain in the early-to-mid Circular series. Annual or multi-year statistical compilations sit here, as do economic guidance Circulars.

Representative Circulars:

• Cir 269 — Implications of Airline Codesharing. Economic / regulatory analysis cited from Doc 8335.
• Cir 295 (Article 83 bis) — Guidance on the Implementation of Article 83 bis of the Chicago Convention. Cited from Doc 8335 (Manual on Continuing Airworthiness) and Doc 9379 (Manual of Procedures for Establishment and Management of a State's Personnel Licensing System) for the cross-border legal-responsibility context.
• Annual fleet, traffic, and financial data Circulars issued by the ICAO Air Transport Bureau.

Domain character: economic regulation, codesharing, charging, statistics. Anchored in Doc 9082, Doc 9587, Doc 9626.

Domain 6 — Facilitation and Security#

Circulars supporting Annex 9 (Facilitation) and Annex 17 (Security): machine-readable travel documents, passenger data exchange, security audit guidance, and state-letter follow-ups.

Domain character: border control, travel documents, security oversight. Anchored in Annex 9 and Annex 17.

Domain 7 — Training and Personnel Licensing#

Circulars supporting language proficiency, instructor training, and specific licence endorsements.

Representative Circulars:

• Cir 323 — Guidelines for Aviation English Training Programmes. Underpins Annex 1 / Annex 10 Volume II language proficiency implementation across ATC and flight crew.

Domain character: language proficiency, training programme design, competency-based training and assessment. Anchored in Annex 1 and PANS-TRG (Doc 9868).

Domain 8 — Special Situations and Transitions#

Circulars produced for one-off operational situations or to bridge a SARP transition.

Representative Circulars:

• Cir 328 — Unmanned Aircraft Systems (UAS). Foundational ICAO position paper that seeded later Annex 2 and Annex 7 amendments and Doc 10019 (RPAS Manual).
• Cir 331 — Coordinated Universal Time (UTC) Use in International Civil Aviation. Continuity-of-time-reference guidance for ATM, CNS, and timing-critical systems.
• AIS-to-AIM transitional guidance Circulars issued ahead of Annex 15 Amendment 40 and the publication of Doc 10066 (PANS-AIM).

Domain character: emerging or transitioning regimes; the publication type for "what we know now" before the Annex/PANS catches up.

Cross-domain note#

Domains are descriptive, not prescriptive. ICAO does not assign a domain code to a Circular. The grouping above mirrors how the catalogue is used in regulatory, training, and ANSP work — and how this workspace cross-references Circulars from other topic files.

This file is the Circulars equivalent of the asbu Threads view: it groups Circulars by the kind of work the document is doing, rather than by subject matter. Subject domains are covered in blocks.md.

A Circular usually serves one of six recurring use-cases. Recognising the use-case is the fastest way to judge how to read and cite a given Circular.

Use-case 1 — Methodology / derivation studies#

A Circular publishes the analytical or statistical work that underpins a numerical value or rule found in a SARP or PANS.

Representative example:

• Cir 120 — Methodology for the Derivation of Separation Minima Applied to the Spacing Between Parallel Tracks. The derivation behind parallel-route lateral separation values used in Annex 11 Attachment material (Annex 11 (Air Traffic Services), Attachment A). Doc 9426 (ATS Planning Manual) further references it for traffic behaviour at turns (Doc 9426 (ATS Planning Manual), Part II — see the protected-airspace tables citing "Circular 120, 4.4").

How to read: the Annex gives the rule; the Circular gives the mathematics. Use the Circular when justifying or adapting the rule for a non-standard environment.

Use-case 2 — Case studies and special-situation analysis#

A Circular publishes detailed analysis of a single aircraft type, a single incident class, or a single operating environment whose specifics warrant a stand-alone document.

Representative examples:

• Cir 327 — Wake Turbulence Aspects of Airbus A380-800. Aircraft- specific wake turbulence guidance issued ahead of Doc 4444 wake separation amendments.
• Cir 344 — Education, Training and Reporting Practices Related to Fume Events. Single-event-class guidance covering reporting, training, and follow-up for fume / smoke events.
• Cir 328 — Unmanned Aircraft Systems (UAS). Single-emerging- domain analysis that defined ICAO's first comprehensive position on unmanned aviation.

How to read: the case-study Circular is usually the most authoritative single source on the specific subject for a window of years until the material is absorbed into Annexes or manuals.

Use-case 3 — Statistical compilations and reviews#

A Circular publishes traffic, fleet, financial, or operational statistics on a recurring basis. Numerically a large fraction of the catalogue, particularly in the early-to-mid number ranges and across the Air Transport Bureau output.

Representative examples:

• Annual world fleet, traffic, and financial data compilations.
• Periodic statistical reviews of accidents, occurrences, and safety trends used as inputs to the Global Aviation Safety Plan (GASP).
• Periodic environmental data compilations feeding into the ICAO Environmental Report cycle.

How to read: statistical Circulars are reference data, not policy. Cite the year of issue, since the underlying tables refresh.

Use-case 4 — Transitional / interim guidance#

A Circular bridges the gap between a SARP regime that is changing and the new regime that is not yet fully published.

Representative examples:

• AIS-to-AIM transitional Circulars issued ahead of Annex 15 Amendment 40 and Doc 10066 (PANS-AIM).
• Early PBN / GNSS-RNAV guidance that preceded Doc 9613 (PBN Manual) — see Cir 295 in its PBN context.
• UAS guidance preceding the formal Annex amendments and Doc 10019 (RPAS Manual) — see Cir 328.

How to read: a transitional Circular has a defined shelf life. Once the target SARP / manual is published, the Circular is normally superseded. Always check the target document for the current status.

Use-case 5 — Panel / working-group output#

A Circular publishes the deliverables of an ICAO panel or working group when those deliverables are useful to States but are not themselves SARP material.

Representative examples:

• Cir 330 — Civil/Military Cooperation in Air Traffic Management — output of the Civil/Military Cooperation Working Group; FUA, ATM security, State-aircraft procedures.
• Cir 314 — Threat and Error Management in ATC — output of the human-factors work supporting ATCO competency and PANS-TRG (Doc 9868) Part II Section 1 Chapter 6.
• Cir 351 — En-route Navigation Strategy (Eleventh Edition) — output of the Navigation Systems Panel work on PBN, RNP, and conventional NAVAID rationalisation.

How to read: panel-output Circulars carry the technical authority of the issuing panel. They are the "best position ICAO has on this topic right now" pending any subsequent SARP work.

Use-case 6 — Audit, oversight and economic policy guidance#

A Circular publishes guidance supporting an ICAO audit programme, an economic regulatory message, or a Council-driven policy.

Representative examples:

• Cir 335 — Manual on the USOAP-CMA. Audit-protocol material including ANS Protocol Questions (PQs).
• Cir 295 (Article 83 bis context) — Guidance on the Implementation of Article 83 bis of the Chicago Convention. Cross-border operating-responsibility guidance cited from Doc 8335 and Doc 9379.
• Cir 269 — Implications of Airline Codesharing. Economic guidance cited from Doc 8335.
• Cir 331 — UTC in International Civil Aviation. Reference-time guidance supporting timing-critical systems.

How to read: oversight-and-policy Circulars sit alongside Doc 9082 (charging), Doc 9587 (economic regulation), Doc 9626 (regulation of international air transport), and Doc 9734 (safety oversight) as the operational expression of Council and ANC policy.

Cross-cutting observations#

• A single Circular often serves more than one use-case. Cir 328 (UAS) is both a panel output and a transitional guidance document. Cir 314 (TEM) is both panel output and a methodology study.
• Statistical Circulars normally do not cross use-cases — they stay in compilation mode.
• Use-case 1 (methodology) and use-case 4 (transitional) are the two use-cases most likely to be cited by name from inside an Annex or PANS. The other use-cases tend to be cited only from manuals or external CAA advisory material.

What a Circular is, structurally#

This file is the Circulars equivalent of the asbu Modules view: it treats a single Circular as a "module" and describes its anatomy. A Circular is a deliverable of ICAO publication work — it is funded, produced, reviewed, edited, sold, indexed, and superseded as a unit.

Identifier convention:

Format:    Cir <NNN> [AN/<MMM>]
Examples:  Cir 314 AN/178
           Cir 328 AN/190
           Cir 330 AN/189
           Cir 351                 (Eleventh Edition; AN/ may be omitted)

A Circular is not amended in place. If the underlying material needs revision, ICAO either re-issues the Circular at a higher edition number, supersedes it with a new Circular, or absorbs the material into a manual or Annex.

Standard structural elements#

The body of a Circular generally carries the following elements. Not every Circular includes every element, but the order is conventional.

1. Title block#

• Full title.
• Circular number (Cir N) and AN/ working number.
• Edition number (where applicable).
• Publication year.
• ISBN.
• ICAO logo and "Approved by the Secretary General and published under his authority" (or equivalent issuing-authority statement).

2. Foreword#

The most important section for citation work. The foreword states:

• Purpose — what gap in the existing publication set this Circular fills.
• Scope — what is and is not covered.
• Audience — States, ANSPs, operators, training organisations, academia, etc.
• Status — explicit reminder that the Circular is informational, not SARP.
• Origin — the panel, study group, or Secretariat division that produced the material.
• Relationship to other ICAO documents — Annexes referenced, PANS referenced, Docs referenced, prior Circulars superseded.

3. Glossary / definitions#

Subject-specific definitions that diverge from or supplement the definitions in Doc 9713 (ICAO Vocabulary), Annex 1 definitions, and Annex 11 definitions. The glossary is binding within the Circular but does not amend the master ICAO definitions.

4. Main body#

The technical content — typically organised as numbered chapters with sub-sections. Most Circulars use a hierarchical numbering scheme (1., 1.1, 1.1.1) consistent with Annex / PANS conventions to make cross-references readable.

5. Appendices#

Supporting material:

• Methodology derivations (Cir 120-style mathematics).
• Sample reporting templates (Cir 344-style).
• Best-practice case studies (Cir 330-style civil/military examples).
• Tabular data (statistical Circulars).
• Cross-reference matrices to Annexes / PANS.

6. References#

A formal list of cited documents — Annexes, PANS, Doc-series manuals, prior Circulars, and external standards (RTCA DO, EUROCAE ED, ISO, ITU). External citations are normally given in author-style format.

The "purpose, scope, audience, status" block#

A useful exercise when reading a Circular is to extract a four-line summary from the foreword:

• Purpose — one sentence on what problem this Circular addresses.
• Scope — what operations / domains / aircraft are covered.
• Audience — who should read it.
• Status — informational; relationship to SARPs.

For Cir 328 (UAS):

• Purpose: provide initial ICAO guidance on integration of unmanned aircraft into international civil aviation.
• Scope: international flight by unmanned aircraft; not model aircraft; not autonomous aircraft.
• Audience: regulators, ANSPs, operators, manufacturers.
• Status: informational; precedes Annex 2 / Annex 7 amendments and Doc 10019 (RPAS Manual).

For Cir 330 (Civil/Military Cooperation):

• Purpose: codify best practice for civil/military cooperation in ATM.
• Scope: airspace planning, FUA, ATM security, State aircraft, joint use of CNS.
• Audience: civil ANSPs, military ATS providers, regulators.
• Status: informational; complements Annex 11 and Doc 4444 provisions on ATS and airspace organisation.

Worked anatomy — Cir 314 (Threat and Error Management)#

• Title block. "Threat and Error Management (TEM) in Air Traffic Control", Cir 314 AN/178, single edition.
• Foreword. States that TEM has been adopted by the operational community as a normalising framework for human performance and that this Circular extends prior flight-deck TEM material to the ATC environment. References PANS-TRG (Doc 9868) Part II Section 1 Chapter 6 and the glossary entry that uses Cir 314 to define "undesired states".
• Glossary. Terms specific to TEM in ATC: threat, error, undesired state, countermeasure.
• Main body. TEM model description applied to ATC; data collection (Normal Operations Safety Survey, NOSS — itself documented in Doc 9910); examples; performance implications.
• Appendices. Sample observation forms, classification taxonomy.
• References. Annex 1, PANS-TRG (Doc 9868), Doc 9910 (NOSS).

Worked anatomy — Cir 120 (Parallel-track separation)#

• Title block. "Methodology for the Derivation of Separation Minima Applied to the Spacing Between Parallel Tracks in ATS Route Structures", Circular 120.
• Foreword. Explains that the Circular is the supporting study for parallel-track separation values that appear in Annex 11 (Air Traffic Services), Attachment material on route spacing.
• Glossary. Containment probability, lateral overlap, system performance, navigation accuracy.
• Main body. VOR-based and RNAV-based derivations; the 95 per cent containment basis; behaviour at turns.
• Appendices. Mathematical derivations; tables of protected airspace; correction factors for traffic-density variants.
• References. Annex 10 (Aeronautical Telecommunications) Vol I; Annex 11; Doc 4444 (PANS-ATM); Doc 9426 (ATS Planning Manual).

How a Circular becomes a national document#

Two patterns dominate:

1. CAA advisory material. A national CAA issues an advisory circular or guidance material that adopts the Circular's methodology by reference. Common for Cir 314 (TEM training), Cir 323 (aviation English), Cir 327 (wake aspects), Cir 330 (civ/mil).
2. ANSP procedure absorption. An ANSP rewrites a Circular's appendix templates into its own procedure or training syllabus. Common for Cir 314 (NOSS observation forms) and Cir 344 (fume-event reporting).

In both patterns, the Circular itself is referenced by number in the national document so that traceability back to ICAO is preserved.

What "enablers" means here#

In the asbu framework, "enablers" are the supporting elements without which a module cannot deliver. Adapted to Circulars, the equivalent question is: who originates a Circular, and what review path does it travel before publication. A Circular without an originating body cannot exist; that body's authority is what gives the Circular its weight despite the lack of SARP status.

ICAO Circulars are originated by one or more of: an Air Navigation Commission (ANC) panel, an ANC working group or study group, a Secretariat bureau, or a Council-mandated working group.

1. Air Navigation Commission (ANC) and its panels#

The Air Navigation Commission is the technical organ of ICAO. Most operational and technical Circulars trace their origin to one of its panels or study groups. Selected panels relevant to ATM Circulars:

• Separation and Airspace Safety Panel (SASP). Originator of separation-methodology material. Underpinning study for the parallel-track separation guidance later published in Cir 120 came from SASP and predecessor groups.
• Air Traffic Management Operations Panel (ATMOPSP). Originator of ATFM, A-CDM, network operations, and FUA material.
• Operations Panel (OPSP) and the human-factors stream. Originator of Cir 314 (TEM in ATC) and related human-performance Circulars.
• Remotely Piloted Aircraft Systems Panel (RPASP) (and predecessor Study Group, UASSG). Originator of Cir 328 and the subsequent amendments and Doc 10019.
• Navigation Systems Panel (NSP) and Communications Panel (CP) and Surveillance Panel (SP). Originators of CNS-related Circulars including Cir 351 (En-route Navigation Strategy).
• Flight Operations Panel (FLTOPSP). Originator of operational Circulars on flight operations, all-weather operations, and similar topics.
• Meteorology Panel (METP). Originator of MET-related Circulars feeding into Annex 3 and Doc 10157 (PANS-MET).
• Aerodromes Panel (AP). Originator of aerodrome-related Circulars feeding into Annex 14 and Doc 9981 (PANS-Aerodromes).
• Aeronautical Information Management Panel (AIMP). Originator of AIS-to-AIM transitional Circulars feeding into Annex 15 and Doc 10066 (PANS-AIM).
• Dangerous Goods Panel (DGP), Aviation Security Panel (AVSECP), Facilitation Panel (FALP). Originators of DG / security / facilitation Circulars.

Panel-originated Circulars normally carry an explicit acknowledgement of the originating panel in the foreword.

2. ANC working groups and study groups#

Smaller bodies, sometimes ad hoc, that report into a panel or directly to the ANC. Relevant examples for ATM:

• Civil/Military Cooperation Working Group. Originator of Cir 330 (Civil/Military Cooperation in Air Traffic Management).
• Wake Turbulence Working Group / RECAT working groups. Originators of Cir 327 (A380 wake) and feeding into RECAT-ICAO.
• Threat and Error Management Study Group. Originator of the TEM-in-ATC material in Cir 314.
• Language Proficiency Study Group. Originator of Cir 323 (aviation English).
• AIS-AIM Study Group (AIS-AIMSG). Originator of the AIS-to-AIM transitional Circulars and the work that produced Doc 10066.
• Cabin Safety Group. Originator of Cir 344 (fume events).
• GNSS Implementation Study Group / PBN Study Group. Originator of early GNSS-RNAV / PBN guidance later absorbed into Doc 9613.

A working-group Circular is normally co-issued with explicit reference to the parent panel and to the ANC review that approved publication.

3. ICAO Secretariat bureaux#

Three Secretariat bureaux originate Circulars:

• Air Navigation Bureau (ANB). The bureau most ATM Circulars flow through; runs the technical panels listed above and provides the AN/ working number on each Circular's title block.
• Air Transport Bureau (ATB). Originator of statistical Circulars (fleet, traffic, finance), economic-policy Circulars, and facilitation Circulars. Doc 9626 (Manual on the Regulation of International Air Transport) records that ATB supports CNS/ATM and ASBU implementation; the parallel ATB-originated Circulars carry the economic and statistical material.
• Bureau of Administration and Services (ADB). Originator of administrative Circulars and certain audit-programme Circulars.

The Secretariat path is also used for Council-mandated Circulars — for example, audit-programme guidance like Cir 335 (USOAP-CMA) and economic policy material such as Cir 269 (codesharing), Cir 295 (Article 83 bis implementation).

4. The ANC and Council review path#

The path from drafting to publication typically follows:

1. Originating body (panel / working group / Secretariat) drafts the Circular.
2. Internal Secretariat review for editorial consistency, Annex / PANS alignment, and translation readiness.
3. ANC review for technical Circulars — the ANC notes the document and approves publication where required. For purely informational compilations the Secretariat may publish under the Secretary General's authority without formal ANC review.
4. Council action for Council-mandated material (audit programmes, economic policy, facilitation policy).
5. Publication through the ICAO Publications service. Circular appears in the catalogue and on the ICAO Store.
6. Distribution to States via State Letter, regional offices, and the Publications system.

The foreword of each Circular usually identifies which steps were formally taken so that the reader can judge the level of ICAO endorsement.

5. Regional offices and PIRGs#

ICAO Regional Offices (APAC, MID, EUR/NAT, AFI, NACC, SAM, WACAF) and their associated Planning and Implementation Regional Groups (PIRGs — APANPIRG, MIDANPIRG, EANPG, etc.) are normally consumers of Circulars rather than originators. They do, however, contribute case material that informs Circulars (e.g. APAC operational data feeding into civil/military and ATFM Circulars; MID operational data feeding into ATM-security material).

6. External technical-standards bodies#

ICAO Circulars often reference and build on output from:

• RTCA (US) — DO-series MOPS for avionics.
• EUROCAE (EU) — ED-series MOPS for avionics.
• ITU — radio-frequency allocations for CNS.
• ISO — terminology and data-format standards.
• Industry coordination bodies — IATA, CANSO, ACI.

These are not originators of Circulars but supply technical content that Circulars build on, and they are routinely cross-referenced in Circular bibliographies.

How originating-body identity affects how a Circular is used#

• A panel-originated Circular has the strongest technical authority in its domain. CAAs commonly adopt its methodology by reference.
• A working-group-originated Circular is treated similarly to a panel output but is sometimes superseded faster if the parent panel later produces a manual.
• A Secretariat-originated statistical Circular is a reference-data document — cite the year of issue.
• A Council-mandated Circular sits next to Council Doc-series policy papers and is often cited from those Docs (Doc 9587, Doc 9082, Doc 9626) by Circular number.

How a non-SARP document supports performance#

ICAO Circulars carry no SARP weight. They impose no obligation under Article 38 of the Chicago Convention. States do not file differences against them. Yet Circulars play a structural role in the wider performance, safety, and implementation frameworks of ICAO. This file maps that role.

The defining contribution of a Circular is information dissemination — turning panel work, statistical data, study results, and transitional guidance into a citable, distributable document with a stable number. Information dissemination is itself a performance enabler: a SARP that is poorly understood is a SARP that is poorly implemented.

Three frameworks that depend on Circulars#

1. Global Aviation Safety Plan (GASP) — Doc 10004#

GASP sets State and regional safety performance targets and identifies the safety enhancement initiatives needed to meet them. Circulars contribute to GASP in three ways:

• Methodology supply. Cir 314 (TEM in ATC) supplies the human- performance methodology that PANS-TRG (Doc 9868) Part II Section 1 Chapter 6 anchors and that ATCO competency frameworks rest on.
• Audit-programme support. Cir 335 (USOAP-CMA) carries the audit protocols including ANS Protocol Questions used to score State safety oversight effectiveness — a direct GASP indicator.
• Occurrence-class guidance. Cir 344 (fume events) and similar occurrence-class Circulars feed safety-data programmes and inform GASP targets.

2. Global Air Navigation Plan (GANP) — Doc 9750#

GANP and the ASBU framework underneath it specify operational and technical improvements organised by Block, Thread, and Module. Many ASBU modules cite Circulars in their supporting-material lists:

• NAVS / APTA threads. Reference Cir 351 (En-route Navigation Strategy) and the body of PBN Circulars absorbed into Doc 9613.
• WAKE thread. References Cir 327 (A380 wake) as part of the RECAT-ICAO development trail.
• FRTO / NOPS threads. Reference Cir 330 (Civil/Military Cooperation) for the FUA and ATM-security context that en-route modernisation depends on.
• DAIM thread. References the AIS-to-AIM transitional Circulars that preceded Annex 15 Amendment 40 and Doc 10066 (PANS-AIM).
• RPAS thread. References Cir 328 (UAS) as the foundational ICAO position before Annex amendments and Doc 10019.

A Circular cited from an ASBU module is treated as supporting material — not an enabler in the SARP sense, but a citable source for States preparing implementation plans.

3. Global Aviation Security Plan (GASeP) and Annex 17 framework#

GASeP and the Aviation Security Panel produce Circulars on screening, landside security, and emerging-threat analysis. These follow the same pattern as GASP: Council-mandated framework + panel-originated Circulars that disseminate methodology and case material.

How performance is measured against Circular content#

A Circular cannot be "implemented" in the SARP sense. There is no declared compliance state. Instead, three indirect performance measures apply:

Measure 1 — Adoption rate by States#

How many States cite the Circular in their national rule, advisory circular, or oversight checklist. ICAO uses USOAP-CMA results and State Letter responses to gauge adoption of selected Circulars (notably Cir 314 for TEM, Cir 335 for audit protocols, Cir 323 for language proficiency programmes).

Measure 2 — Maturity into a SARP / PANS / Manual#

The strongest signal that a Circular has done its job is when its content is absorbed into a higher-status publication. The Cir 113 → Doc 9328 (RVR) trajectory, the Cir 295 → Doc 9613 (PBN) trajectory, and the Cir 328 → Doc 10019 + Annex amendments (RPAS) trajectory are canonical examples.

Measure 3 — Citation density inside the SARP / PANS / Doc set#

How often the Circular is referenced from inside other ICAO publications. Cir 120 is cited from Annex 11 (Air Traffic Services), Attachment material on parallel-track derivation; Cir 314 is cited from PANS-TRG (Doc 9868) §Part II Section 1 Chapter 6 and from Annex 1 (Personnel Licensing) Notes; Cir 295 (Article 83 bis) is cited from Doc 8335 (Manual on Continuing Airworthiness) and Doc 9379 (Manual on Personnel Licensing). Citation density indicates how load-bearing the Circular has become in the wider corpus.

Key Performance Areas (KPAs) most affected#

Mapping Circular dissemination onto the eleven KPAs from Doc 9854 / Doc 9883:

• Safety. Strongest connection. Cir 314 (TEM), Cir 335 (USOAP-CMA), Cir 344 (fume events).
• Capacity / Flight efficiency. Cir 120 (parallel tracks), Cir 327 (A380 wake / RECAT input), Cir 351 (en-route navigation strategy), Cir 330 (FUA / civ-mil airspace release).
• Cost-effectiveness. Cir 269 (codesharing), Cir 295 (Article 83 bis), audit-programme Circulars supporting Doc 9587 economic- regulation policy.
• Interoperability. AIS-to-AIM transitional Circulars feeding Doc 10066 (PANS-AIM) and Annex 15 Amendment 40.
• Access and equity. Cir 323 (aviation English) supporting Annex 1 / Annex 10 Vol II language proficiency requirements.
• Environmental impact. Annex 16 (Environmental Protection) background Circulars on emissions and noise inventories.

Why Circulars matter to a State performance plan#

A State's air-navigation performance plan (national ANP, State Safety Programme, State Action Plan on environment) cites Annexes, PANS, and manuals as the "what" and "how". Circulars typically appear in such plans in two ways:

• As supporting evidence. "Methodology per Cir 120" or "Training framework per Cir 314".
• As gap-filler for emerging topics. Until the relevant Annex amendment is in force, Circulars are the only ICAO position available — typical for UAS, drone integration, urban air mobility, and other emerging domains.

In both modes, the Circular plays a performance role even though no performance indicator measures the Circular itself. The indicators measure the operational outcome the Circular's methodology produces.

Two timelines to keep distinct#

When discussing Circular "dates", separate two things:

1. Issue date — when ICAO first published the Circular under that number.
2. Active life — the period during which the Circular is the primary ICAO position on its subject. Active life ends when the material is absorbed into a higher-status publication or when the Circular is withdrawn.

A Circular's number is a permanent identifier. Withdrawal does not re-use the number. The series therefore grows monotonically; gaps in the visible catalogue indicate withdrawn or superseded Circulars.

The shape of the series#

Numbering runs from Cir 1 (early 1940s, post-Provisional ICAO and early ICAO years) through the current mid-300s. The series is single-stream — all subjects share one number space.

1940s -------- 1960s -------- 1980s -------- 2000s -------- 2020s
Cir 1 -----+   Cir 100s ---+  Cir 200s ---+ Cir 300s ----+--->
           |               |               |              |
        Early stats     Cir 113 (RVR)  Cir 269         Cir 314 (TEM)
        and procedural  Cir 120        (codeshare)     Cir 327 (A380)
        material        (parallel      Cir 295         Cir 328 (UAS)
                        tracks)        (Art 83 bis,    Cir 330 (Civ/Mil)
                                       and PBN)        Cir 331 (UTC)
                                                       Cir 335 (USOAP-CMA)
                                                       Cir 344 (fume)
                                                       Cir 351 (en-route
                                                       NAV strategy)

The cadence is irregular. ICAO does not publish a fixed number of Circulars per year. Issuance follows panel and Secretariat workload.

Notable Circulars across the series#

Early / mid-series (Cir 1 through Cir 200)#

• Cir 113 — Visibility and Runway Visual Range. Foundational RVR material; matured into Doc 9328 (RVR Manual). Doc 9328 itself records that the original methodology came from this Circular.
• Cir 120 — Methodology for the Derivation of Separation Minima Applied to the Spacing Between Parallel Tracks. The mathematical basis for parallel-track lateral separation. Cited from Annex 11 (Air Traffic Services), Attachment material on route spacing, and from Doc 9426 (ATS Planning Manual) — including the explicit table reference "Circular 120, 4.4" in Doc 9426.

Cir 200 series (economic, statistical, operational)#

• Cir 269 — Implications of Airline Codesharing. Economic / regulatory analysis cited from Doc 8335 (Manual on Continuing Airworthiness) Note 2 alongside Doc 9626 (Manual on the Regulation of International Air Transport).
• Cir 295 — Two distinct Circulars share this number across contexts. One is the Guidance on the Implementation of Article 83 bis of the Chicago Convention, cited from Doc 8335 and Doc 9379 (Manual of Procedures for Establishment and Management of a State's Personnel Licensing System). The other is the early GNSS-RNAV / PBN guidance subsequently absorbed into Doc 9613 (PBN Manual). Always verify by full title.

Cir 300 series (modern operational and safety)#

• Cir 314 (AN/178) — Threat and Error Management (TEM) in Air Traffic Control. Issued 2008. Anchors TEM in the ATC environment and is cited from PANS-TRG (Doc 9868) §Part II, Section 1, Chapter 6 and from Doc 9868 glossary entries on threat management. Also cited from Annex 1 (Personnel Licensing) Notes alongside the PANS-TRG reference. Active and load-bearing.
• Cir 323 — Guidelines for Aviation English Training Programmes. Issued 2009. Supports Annex 1 / Annex 10 Vol II language proficiency requirements; widely adopted by State CAAs and training organisations.
• Cir 327 — Wake Turbulence Aspects of Airbus A380-800. Issued ahead of Doc 4444 wake separation amendments and feeding into RECAT-ICAO. Type-specific case study.
• Cir 328 (AN/190) — Unmanned Aircraft Systems (UAS). Issued 2011. Foundational ICAO position paper on integration of unmanned aircraft into international civil aviation. Seeded the Annex 2 / Annex 7 amendments and Doc 10019 (RPAS Manual).
• Cir 330 (AN/189) — Civil/Military Cooperation in Air Traffic Management. Issued 2011. Codifies best practice for FUA, ATM security, State-aircraft procedures, and joint use of CNS.
• Cir 331 — Coordinated Universal Time (UTC) Use in International Civil Aviation. Continuity-of-time-reference guidance for ATM, CNS, and timing-critical systems.
• Cir 335 — Manual on the USOAP Continuous Monitoring Approach (USOAP-CMA). Audit-protocol material covering State safety oversight including the ANS Protocol Questions used in audits.
• Cir 344 — Guidelines on Education, Training and Reporting Practices Related to Fume Events. Cabin-air-quality safety reference cited in occurrence-handling and CRM training material.
• Cir 351 — En-route Navigation Strategy (Eleventh Edition). Strategic guidance on PBN, RNP, conventional NAVAID rationalisation, and the future en-route navigation environment.

(Numbering between the examples above is occupied by other Circulars covering security, facilitation, environment, and statistics.)

Maturation patterns#

A useful lens on the timeline is the maturation of Circular material into higher-status publications.

Maturation does not always retire the Circular. Cir 314 remains active and is cited from PANS-TRG even though TEM is now embedded in ATCO competency frameworks. Cir 120 remains the citable methodology behind Annex 11 values.

Reading a date in a Circular#

When a Circular cites a date, check which kind of date it is:

• Issue year on the title page — the publication date for that edition.
• Edition number (e.g. "Eleventh Edition" on Cir 351) — indicates prior editions exist; check the foreword for predecessor numbering.
• References to Annex amendment dates — these float as the cited Annex is amended; treat them as snapshots at the Circular's issue date.
• References to PANS amendment dates — same caveat.

The most stable reference is the Circular number itself plus the edition number, if any.

How the catalogue is consulted today#

• ICAO Publications portal (https://www.icao.int/publications) exposes the catalogue with subject filters.
• ICAO Store (https://store.icao.int) handles purchase and digital download.
• SKYbrary bookshelf (https://skybrary.aero/bookshelf) mirrors selected Circulars (notably Cir 328 UAS and Cir 330 Civ/Mil) for open access.
• Inside Annexes, PANS, and Doc-series manuals — most active Circulars are cited by number from at least one higher-status publication, and that citation is normally the most reliable pointer.

Primary publication portals#

• ICAO Publications portal — https://www.icao.int/publications — the master entry to ICAO publication categories (Annexes, PANS, Doc-series, Circulars).
• ICAO Store — https://store.icao.int — purchase and digital download of Circulars by number, title, or subject.
• SKYbrary bookshelf — https://skybrary.aero/bookshelf — open mirror of selected Circulars (notably Cir 328 UAS, Cir 330 Civ/Mil, Cir 314 TEM where available).
• ICAO Annual Report — Annex/PANS Amendments, Manuals and Circulars — https://www.icao.int/annual-report — yearly summary of new and amended Circulars.

ICAO documents that anchor the publication hierarchy#

• Chicago Convention (1944) — the legal basis for SARPs and the reason Circulars carry no Article 38 obligation.
• Annexes 1–19 — the SARP layer; many Annexes cite specific Circulars in Notes or Attachments.
• PANS — Doc 4444 (PANS-ATM), Doc 8168 (PANS-OPS), Doc 9868 (PANS-TRG), Doc 8400 (PANS-Abbreviations and Codes), Doc 10066 (PANS-AIM), Doc 10157 (PANS-MET), Doc 9981 (PANS-Aerodromes). Procedures elaborating SARPs; common citation source for Circulars.
• Doc 7030 — Regional Supplementary Procedures.
• Doc 9082 — Policies on Charges for Airports and Air Navigation Services — Council policy for charging.
• Doc 9587 — Policy and Guidance Material on the Economic Regulation of International Air Transport — anchors economic Circulars including Cir 295 (Article 83 bis).
• Doc 9626 — Manual on the Regulation of International Air Transport — frequently cited alongside economic Circulars.
• Doc 9750 — Global Air Navigation Plan (GANP) — the framework whose ASBU modules cite Circulars as supporting material.
• Doc 10004 — Global Aviation Safety Plan (GASP).
• Doc 9854 — Global ATM Operational Concept.
• Doc 9883 — Manual on Global Performance of the Air Navigation System.

Representative Circulars by number#

The list below is the working catalogue used elsewhere in this folder. Subject indications are short; consult the ICAO Store for the full title and current status.

Operational / ATM#

• Cir 120 — Methodology for the Derivation of Separation Minima Applied to the Spacing Between Parallel Tracks in ATS Route Structures. Cited from Annex 11 (Air Traffic Services), Attachment material on parallel-track separation, and from Doc 9426 (ATS Planning Manual).
• Cir 327 — Wake Turbulence Aspects of Airbus A380-800.
• Cir 328 (AN/190) — Unmanned Aircraft Systems (UAS). Foundational; superseded operationally by Doc 10019 (RPAS Manual) and Annex 2 / Annex 7 amendments.
• Cir 330 (AN/189) — Civil/Military Cooperation in Air Traffic Management. SKYbrary summary: https://skybrary.aero/bookshelf/civilmilitary-cooperation-air-traffic-management-icao-circ330
• Cir 331 — Coordinated Universal Time (UTC) Use in International Civil Aviation.

Safety and human performance#

• Cir 314 (AN/178) — Threat and Error Management (TEM) in Air Traffic Control. Cited from PANS-TRG (Doc 9868), §Part II, Section 1, Chapter 6, and from Annex 1 (Personnel Licensing) Notes.
• Cir 335 — Manual on the USOAP Continuous Monitoring Approach (USOAP-CMA).
• Cir 344 — Guidelines on Education, Training and Reporting Practices Related to Fume Events.

CNS / Navigation#

• Cir 113 — Visibility / Runway Visual Range. Matured into Doc 9328 (RVR Manual).
• Cir 295 (PBN context) — Guidelines for the Implementation of GNSS-aided RNAV. Substantially absorbed into Doc 9613 (PBN Manual).
• Cir 351 — En-route Navigation Strategy (Eleventh Edition).

Economics, statistics, and Council policy#

• Cir 269 — Implications of Airline Codesharing. Cited from Doc 8335 Note 2.
• Cir 295 (Article 83 bis context) — Guidance on the Implementation of Article 83 bis of the Convention on International Civil Aviation. Cited from Doc 8335 (Manual on Continuing Airworthiness) and Doc 9379 (Manual of Procedures for Establishment and Management of a State's Personnel Licensing System). Note that "Cir 295" thus appears in two distinct contexts in the cited literature; verify by full title.

Training and licensing#

• Cir 323 — Guidelines for Aviation English Training Programmes.

Special-situation and transitional (representative)#

• AIS-to-AIM transitional Circulars — preceded Annex 15 Amendment 40 and Doc 10066 (PANS-AIM); superseded operationally on the entry into force of Doc 10066.

Open-access / external mirror sources#

• Cir 328 (UAS) — open PDF mirror — https://skybrary.aero/sites/default/files/bookshelf/3202.pdf
• Cir 330 (Civ/Mil) — SKYbrary summary page — https://skybrary.aero/bookshelf/civilmilitary-cooperation-air-traffic-management-icao-circ330
• EUROCONTROL library — https://www.eurocontrol.int/publications — hosts mirror copies of Circulars in the FUA, civil/military, and network-management context.

How to cite a Circular formally#

Use the ICAO publication citation form. Examples in the workspace style:

• Cir 120 (Methodology for Parallel-Track Separation), §4.4 — note on aircraft behaviour at turns.
• Cir 314 (Threat and Error Management in Air Traffic Control) — whole-of-document reference for TEM methodology. Cited from PANS-TRG (Doc 9868), §Part II, Section 1, Chapter 6.
• Cir 328 (Unmanned Aircraft Systems) — foundational ICAO position; superseded operationally by Doc 10019 (RPAS Manual) and Annex 2 / Annex 7 amendments.
• Cir 330 (Civil/Military Cooperation in Air Traffic Management), Appendix B — best-practice examples of joint civil/military airspace coordination.

Where the Circular is not in the local Markdown library but is referenced from a higher-status publication that is, the citation format used elsewhere in this workspace is:

• Cir 120 (Methodology for Parallel-Track Separation) — cited from Annex 11 (Air Traffic Services), Attachment material on parallel tracks (authoritative source — not in local library).