Detailed working notes on the regional realisation of ATS Interfacility Data Communications (AIDC) in the ICAO EUR and MID Regions. This folder expands the summary in topics/aidc_europe_middle_east.md into per-aspect files so each can be read on its own.

The global AIDC baseline (Doc 4444 Chapter 11 and Appendix 6) is covered in the sibling folder topics_detailed/aidc/. This folder focuses on the two regional ICDs that turn that baseline into on-the-wire behaviour: the EUROCONTROL OLDI Specification in Europe and the ICAO MID Region AIDC ICD in the Middle East. Where the EUR/MID seam meets the APAC ICD, this folder also documents the gateway behaviour.

Files in this folder#

• overview.md — what AIDC means in EUR and MID, and how OLDI relates to the ICAO AIDC message set.
• components.md — message sets (OLDI catalogue vs. ICAO AIDC subset used in the MID ICD) and the mapping between them.
• blocks.md — regional ICD editions and OLDI Specification versions treated as time-phased delivery slots.
• threads.md — functional areas of the AIDC dialog: notification, coordination, transfer of control, transfer of communication, revision, abrogation, civil-military.
• modules.md — anatomy of a cross-FIR AIDC dialog between adjacent EUR and MID centres, end to end.
• enablers.md — bearer infrastructure (AFTN, AMHS, ATN, FMTP), LoA negotiation, and the regional bodies that host the ICDs.
• performance_objectives.md — KPAs (interoperability, predictability, capacity, safety) and the KPIs MIDANPIRG and EUROCONTROL track.
• timeline.md — OLDI evolution from Edition 1 (1992) through Edition 5.1 (2023); MID AIDC ICD adoption; cross-region trials.
• references.md — consolidated ICAO, EUROCONTROL, EASA, and MID Office references.

Reading order#

Start with overview.md, then components.md for the message-set detail, then threads.md for the functional decomposition. Use modules.md to walk through a single end-to-end dialog. blocks.md and timeline.md give the version and date context. enablers.md and performance_objectives.md cover the infrastructure and measurement aspects. references.md consolidates citations.

Source basis#

Content is grounded in:

• ICAO Doc 4444 (PANS-ATM), Chapter 11 and Appendix 6 — the global AIDC baseline.
• ICAO Annex 11 (ATS) Chapters 3 and 6 — coordination requirements and ground-ground communication basis.
• ICAO Annex 10 Volume II — AFTN/ATN message handling.
• ICAO Doc 7030 — Regional Supplementary Procedures (EUR, MID).
• ICAO Doc 9694 — Manual of ATS Data Link Applications.
• ICAO Doc 9705 / Doc 9880 / Doc 9896 — ATN and ATN/IPS technical provisions.
• EUROCONTROL Specification for On-Line Data Interchange (OLDI), Edition 5.1 (2023) — authoritative source, not in local library.
• EUROCONTROL Specification for the Flight Message Transfer Protocol (FMTP), Edition 2.0 — authoritative source, not in local library.
• EASA ED Decision 2023/015/R reissuing OLDI as Acceptable Means of Compliance — authoritative source, not in local library.
• ICAO MID Region AIDC ICD, maintained by MIDANPIRG ATM Sub-Group — authoritative source, not in local library.
• MIDANPIRG ATM SG and CNS-SG outcomes; MID Air Navigation Report.

What AIDC is, briefly#

ATS Interfacility Data Communications (AIDC) is the structured ground-ground exchange of flight information between adjacent Area Control Centres for the purposes of notification, coordination, transfer of control, transfer of communication, revision, and abrogation. The global baseline lives in Doc 4444 (PANS-ATM) Chapter 11 and Appendix 6, with the underlying coordination obligation in Annex 11 Chapter 3 and the ground-ground communication basis in Annex 11 Chapter 6 (aeronautical fixed service).

Doc 4444 §11.2.2.2 explicitly anticipates regional realisation: the ATS message set in Appendix 3 "shall be supplemented with, and/or replaced by" the AIDC messages in Appendix 6 on the basis of regional air navigation agreements. The two regional realisations relevant to this folder are:

• EUR — EUROCONTROL Specification for On-Line Data Interchange (OLDI), currently Edition 5.1 (2023).
• MID — ICAO MID Region AIDC ICD, maintained by the MIDANPIRG ATM Sub-Group.

A third realisation, the ICAO Asia/Pacific AIDC ICD, is the de facto reference for the ICAO message subset and is relevant where the EUR/MID seam touches APAC airspace.

Why EUR and MID are treated together#

The two regions share a long FIR seam (Cairo-Athens, Cairo-Nicosia, Tehran-Ankara, Damascus-Nicosia, Beirut-Nicosia, Amman-Nicosia, Jeddah-Khartoum-Cairo, Tehran-Baku-Yerevan-Trabzon arc) on which one side speaks OLDI/FMTP and the other speaks the ICAO AIDC message set over AFTN/AMHS or bilateral IP. The interoperability question — how a flight crossing the seam is notified, coordinated, and transferred without operator workarounds — is the practical reason these two regions are reviewed jointly.

The two regions also have different governance:

• EUR is driven by EUROCONTROL specifications adopted as EASA Acceptable Means of Compliance under EU interoperability rules (Single European Sky Implementing Regulations).
• MID is driven by ICAO regional planning under MIDANPIRG with state-pair Letters of Agreement (LoA) doing the operational binding.

OLDI and ICAO AIDC are not the same thing#

OLDI and the ICAO AIDC message set are functionally equivalent — both implement the same operational concept (notify, coordinate, transfer) — but they are distinct on the wire:

• Different message catalogues. OLDI uses ABI, ACT, REV, LAM, MAC, COD/CDN, civil-military XIN/XRQ/XAP. ICAO AIDC (Doc 4444 Appendix 6 and the MID/APAC ICDs) uses LAM, ABI, CPL, EST, ACP, TOC, AOC, MAC, with different field encodings.
• Different bearers in current practice. OLDI rides on FMTP (TCP/IP peer-to-peer) under EU interoperability rules; ICAO AIDC in MID rides on AFTN/AMHS or bilateral IP, with ATN/IPS as the future target.
• Different governance. OLDI is a EUROCONTROL specification reissued by EASA as AMC; the MID ICD is an ICAO regional ICD endorsed by MIDANPIRG.

The mapping between the two is not loss-less: OLDI MAC and ICAO AIDC MAC have different semantics around assumption of control, and OLDI COD/CDN handling of coordination negotiation does not map one-to-one to ICAO ACP/AOC.

What this folder covers#

• Where the regional ICDs come from and how they relate to Doc 4444 Chapter 11 and Appendix 6.
• The message catalogues in each region and the mapping at the seam.
• The functional decomposition (notification, coordination, transfer of control, transfer of communication, revision, abrogation, civil-military).
• The infrastructure (AFTN/AMHS, FMTP, ATN/IPS) and the LoA process that ties two centres into a working AIDC pair.
• Performance and implementation status as tracked by EUROCONTROL (LSSIP) and MIDANPIRG (Air Navigation Report).

Out of scope here#

The global AIDC baseline (4444 Chapter 11 message-by-message detail, ATN/IPS encoding, AIDC priority on the AFTN, AIDC abbreviation in Doc 8400) belongs in topics_detailed/aidc/. Air-ground data link applications (CPDLC, ADS-C) belong in their own topics. Flight Object Interoperability (EUROCAE ED-133) is referenced where it complements OLDI/AIDC but is not the focus.

Two parallel catalogues#

The regional realisation of AIDC in EUR and MID rests on two distinct message catalogues that implement the same operational concept. This file lists both, then maps between them.

EUR — OLDI message catalogue#

The EUROCONTROL OLDI Specification (Edition 5.1, 2023) defines the following message families. Mnemonics are three letters by OLDI convention.

Civil-civil messages#

• ABI — Advance Boundary Information. Pre-notification of a flight to the receiving unit, typically 15-25 minutes before estimated boundary crossing. Equivalent in role to ICAO AIDC ABI / CPL.
• ACT — Activation. Confirmation of boundary estimate; the receiving unit can plan integration. Equivalent in role to ICAO AIDC EST.
• REV — Revision. Update to a previously sent ABI/ACT (level, estimate, route).
• CDN — Coordination. Proposes a coordination condition (level, point, time) that differs from the ABI/ACT.
• COD — Acknowledgement of CDN. Acceptance of the CDN proposal.
• LAM — Logical Acknowledgement Message. Per-message logical ACK on receipt; underlies OLDI delivery assurance.
• MAC — Message for the Abrogation of Coordination. Cancels a previously coordinated flight (e.g. flight cancelled, route significantly changed).
• PAC — Pre-Activation. Pre-departure activation for very short flights.
• INF — Information. Free-text or structured non-binding info.
• TIM — Time of Initial Movement. Off-block / take-off time.
• SBY / RAP / RJC — standby, request approval, reject.

Civil-military messages#

• XIN — Notification of crossing of restricted/reserved airspace.
• XRQ — Request for crossing.
• XAP — Approval of crossing.
• XCM — Cancellation of crossing.

These are exchanged between civil ATC units and military airspace managers (e.g. AMC cells), and underpin Flexible Use of Airspace.

MID — ICAO AIDC message subset used in the MID ICD#

The MID Region AIDC ICD profiles the ICAO AIDC message set defined in Doc 4444 Appendix 6. The set used on MID seams is typically:

• LAM — Logical Acknowledgement. Per-message logical ACK.
• ABI — Advance Boundary Information.
• CPL — Current Flight Plan. Full flight plan exchange where ABI is insufficient.
• EST — Estimate. Boundary crossing estimate.
• ACP — Application Accept. Acceptance of a coordination request.
• CDN — Coordination message (in MID/APAC profile).
• TOC — Transfer of Control.
• AOC — Assumption of Control.
• MAC — Message for the Abrogation of Coordination.

The MID ICD also defines initiation/connection management messages (LAM, application context establishment) that are necessary on AFTN/AMHS or IP bearers but are not operationally visible to controllers.

Mapping at the EUR/MID seam#

A flight crossing from a EUR FIR (OLDI/FMTP) into a MID FIR (AIDC/AFTN or AIDC/IP) requires either dual-stack FDPS at one or both ends, or a gateway between OLDI and ICAO AIDC primitives. The typical mapping is:

Notes on the mapping:

• Transfer of control is implicit in OLDI (it happens at the Coordination Point with conditions in the LoA) but explicit in the ICAO AIDC message set (TOC/AOC pair).
• MAC semantics differ. OLDI MAC is used to cancel coordination; ICAO AIDC MAC has additional semantics tied to assumption of control.
• Civil-military has no clean ICAO AIDC equivalent. MID seams fall back to AFTN messages and voice coordination for restricted/reserved airspace.
• Free Route Airspace coordination points may be defined as bearing/distance from a known point in OLDI; ICAO AIDC ICDs that assume a named COP at the boundary need extension to handle this, which the MID ICD addresses incrementally.

Components beyond messages#

A complete AIDC implementation includes:

• Connection state machine. Application context establishment, keep-alive, error recovery.
• Addressing. Doc 4444 §11.3.5.1 fixes the rule that the sending unit names the receiving ATS unit and the next ATS unit; OLDI uses unit identifiers and the FMTP endpoint table.
• Time reference. UTC; tolerances on estimate accuracy fixed in the LoA.
• Coordinate Point register. Named COPs (and bearing/distance COPs in FRA) maintained per state-pair LoA.
• Bearer. AFTN/AMHS, FMTP/IP, ATN/IPS, or bilateral IP circuit.
• Logging and replay. For incident review and AIDC performance reporting.

Why "blocks" applies here#

The ASBU framework groups operational improvements into time-phased availability windows. The regional AIDC realisation evolves the same way: each ICD or OLDI edition bundles a set of capabilities that become regionally implementable from a defined date. A new edition matters only if both ends of an AIDC link have adopted it (and the LoA references it), so editions function as compatibility "blocks" in practice.

OLDI editions (EUR)#

Edition dates below reflect the EUROCONTROL publication record; the on-the-wire impact of each edition is filtered through the LoA between the two adjacent ANSPs.

Notes:

• Exact intermediate edition numbers and dates between Edition 1 and Edition 5 vary across EUROCONTROL records; consult the published specification table at eurocontrol.int for the authoritative list.
• Adoption of an OLDI edition by an ANSP is signalled in the LSSIP return and bound bilaterally in the LoA with each neighbour.

FMTP editions (EUR bearer)#

FMTP is the TCP/IP bearer specification that replaced legacy CIDIN/ X.25 for OLDI exchange. It is governed alongside OLDI by EU interoperability rules.

MID Region AIDC ICD editions#

The MID Region AIDC ICD is younger than OLDI and was developed under MIDANPIRG ATM Sub-Group leadership. Edition history is less stable in open sources than OLDI; the following is indicative and should be verified against the latest MIDANPIRG ATM SG outcomes.

The MID ICD is treated as a living document and is amended in step with the regional Air Navigation Performance Indicator (ANPI) for AIDC/OLDI. The ATM SG/11 (2025) outcomes document the current state- pair status.

EUR/MID seam compatibility "blocks"#

For a state-pair on the EUR/MID seam, the practical "block" is the intersection of:

• the EUR side's OLDI + FMTP edition pair;
• the MID side's AIDC ICD version;
• the bearer in use (AFTN/AMHS, bilateral IP, ATN/IPS pilot);
• the LoA-defined message subset and translation rules.

Compatibility regressions when one side upgrades are typically managed by:

• maintaining backward-compatible OLDI/AIDC profiles in the LoA;
• gateway translation at the FDPS level;
• AFTN/voice fallback for messages outside the agreed subset.

Block dependency principle, applied here#

Just as ASBU Block 2 modules depend on Block 0/1 enablers, an AIDC seam upgrade depends on:

• prior AFTN/AMHS reachability and addressing being correct;
• prior LoA covering operational coordination conditions;
• bearer (FMTP / IP / ATN/IPS) being installed and tested;
• both FDPS systems supporting the agreed OLDI/AIDC versions;
• controller training on the new message set or new coordination conditions.

Skipping any of these forces fallback to voice and AFTN, which is exactly what the AIDC/OLDI Priority 1 indicator is designed to discourage.

The AIDC dialog between two adjacent centres is naturally decomposed into functional threads. The same threads apply in EUR (OLDI) and MID (ICAO AIDC), although the message names differ. This file walks through each thread, identifies the OLDI and ICAO AIDC messages involved, and notes the LoA elements that bind it.

The functional threads are:

1. Notification
2. Coordination (including revision)
3. Transfer of Control
4. Transfer of Communication
5. Abrogation
6. Civil-Military Coordination
7. Logical Acknowledgement and Connection Management

1. Notification#

Pre-arrival information from the transferring unit (FIR-1) to the receiving unit (FIR-2) so that FIR-2 can plan integration before the flight reaches the boundary.

• OLDI. ABI message, typically 15-25 minutes before estimated boundary crossing, supplemented by a later ACT.
• ICAO AIDC. ABI for early notification; CPL where the receiving unit has not previously seen the flight plan; EST as the boundary estimate.
• Annex 11 / Doc 4444 basis. Annex 11 §3.7 (notification) and Doc 4444 Chapter 10 coordination obligations.
• LoA elements. Notification timing window; minimum data set; treatment of late or missing notification; fallback to AFTN FPL.

2. Coordination (including revision)#

Negotiation between the two units of the conditions under which the flight will cross the boundary: level, point, time, route. Most flights cross under "standard" conditions defined in the LoA and require no on-the-wire negotiation; non-standard cases trigger explicit messages.

• OLDI. CDN proposes a non-standard condition; COD accepts; REV updates an earlier ABI/ACT.
• ICAO AIDC. CDN/ACP for proposal/accept; CPL or amendment for revision; AOC subsequently confirms assumption.
• Annex 11 / Doc 4444 basis. Annex 11 §3.7 (conditions of transfer); Doc 4444 Chapter 10 (coordination procedures); Doc 4444 §11.3.7 (AIDC negotiation).
• LoA elements. Standard coordination conditions (level band at COP, route segments, climb/descent restrictions); silent transfer rules (where the receiving unit accepts without explicit reply); timer for response.

3. Transfer of Control#

The point at which responsibility for separation passes from FIR-1 to FIR-2.

• OLDI. Implicit at the Coordination Point under conditions fixed in the LoA; no separate message normally required.
• ICAO AIDC. Explicit TOC (Transfer of Control) and AOC (Assumption of Control) message pair.
• Annex 11 / Doc 4444 basis. Annex 11 Chapter 3 (transfer of control conditions); Doc 4444 §10.3 transfer-of-control procedures.
• LoA elements. Geographic point of transfer; level conditions at transfer; whether transfer is conditional (e.g. "after passing FL280 climbing").

4. Transfer of Communication#

The point at which the pilot is instructed to change frequency from FIR-1 to FIR-2.

• OLDI. Not normally a dedicated message; controlled procedurally per LoA.
• ICAO AIDC. May use CPDLC handover messages where data link is in use; otherwise procedural.
• Annex 11 / Doc 4444 basis. Doc 4444 §10.4 transfer of communication.
• LoA elements. Whether communication is transferred simultaneously with control or precedes/follows it; release of frequency procedure; silent handover where applicable.

5. Abrogation#

Cancellation of a previously coordinated flight (cancellation of the flight, large diversion, return-to-departure).

• OLDI. MAC cancels a previously coordinated flight.
• ICAO AIDC. MAC, with semantics tied to assumption of control; the OLDI MAC and ICAO AIDC MAC do not map one-to-one.
• LoA elements. Trigger criteria for sending MAC; required acknowledgement; downstream effect on slot allocation.

6. Civil-Military Coordination#

Notification and approval of crossings of restricted, reserved, or temporarily segregated airspace under Flexible Use of Airspace.

• OLDI. XIN (notification), XRQ (request), XAP (approval), XCM (cancellation). Exchanged with military airspace management cells.
• ICAO AIDC. No clean equivalent in the MID ICD; falls back to AFTN messages and voice coordination.
• Annex 11 / Doc 4444 basis. Annex 11 §2 (FUA and coordination); Doc 4444 Chapter 10.
• LoA elements. Military airspace inventory; activation / deactivation procedures; lead-time requirements.

7. Logical Acknowledgement and Connection Management#

Underlying machinery that keeps the AIDC link healthy.

• OLDI. LAM acknowledges each operational message at the logical layer.
• ICAO AIDC. LAM (Doc 4444 Appendix 6) acknowledges each message; application context establishment manages the connection.
• LoA elements. Acceptable LAM latency; loss-of-comms procedure; fallback to AFTN.

Cross-thread dependencies#

• Notification is a prerequisite for Coordination — a CDN before any ABI/ACT is normally rejected.
• Transfer of Control is conditional on Coordination having been agreed (or being implicit per LoA).
• Civil-Military coordination must complete before a flight enters the relevant airspace, regardless of civil AIDC state.
• LAM and connection management underpin every other thread; loss of the AIDC link forces all threads back to AFTN/voice.

This decomposition is what regional bodies measure: MIDANPIRG and EUROCONTROL track AIDC implementation per thread per state-pair, not just "AIDC up/down".

What this file is#

This walks through a single AIDC dialog end to end, between an EUR centre (OLDI/FMTP) and a MID centre (ICAO AIDC over AFTN/AMHS or bilateral IP), so the message-level detail in components.md and the functional decomposition in threads.md can be seen working together.

The example used is a notional eastbound flight FIR-A (EUR side, OLDI) to FIR-B (MID side, ICAO AIDC), crossing a boundary point COP-1 defined either by a named waypoint or by bearing/distance from a known reference (FRA case).

Pre-conditions#

Before any AIDC message can flow, the following must be in place:

• Letter of Agreement (LoA) between FIR-A and FIR-B covering standard coordination conditions, message subset, response timers, and fallback procedures.
• Reachable AIDC peer. OLDI/FMTP endpoints exchanged and tested on FIR-A side; AIDC application and AFTN/AMHS or IP addresses exchanged on FIR-B side; gateway or dual-stack FDPS bridging the two.
• Common time reference. UTC, with NTP discipline.
• Common COP register. Named COPs and bearing/distance COPs agreed and published per AIP / LoA.
• Controllers trained on the agreed LoA and on the gateway behaviour (what to do when a non-mappable field arrives).

Stage 1 — Filed plan and FDPS preparation#

The flight plan is filed via the IFPS / regional FPL processing system. Both FIR-A and FIR-B FDPSs receive the plan over AFTN. FIR-A's FDPS computes the boundary estimate at COP-1 and identifies FIR-B as the next ATS unit per Doc 4444 §11.3.5.1.

Stage 2 — Notification (ABI)#

Approximately 20 minutes before estimated boundary crossing, FIR-A's FDPS emits an OLDI ABI to FIR-B's FDPS over FMTP. The gateway translates this into an ICAO AIDC ABI for the MID-side FDPS, preserving callsign, type, route segment relevant to FIR-B, and the COP-1 estimate.

FIR-B's FDPS replies with a LAM acknowledging logical receipt. The gateway forwards this back as an OLDI LAM to FIR-A.

Stage 3 — Activation / boundary estimate (ACT / EST)#

A few minutes before COP-1, FIR-A emits an OLDI ACT confirming the boundary estimate. The gateway translates this to an ICAO AIDC EST for FIR-B.

If FIR-B has not previously had the full plan, the gateway can trigger emission of an ICAO AIDC CPL in addition to EST.

Stage 4 — Coordination (standard or non-standard)#

• Standard case. The flight crosses COP-1 at the level band agreed in the LoA. No further messages are required; transfer of control happens implicitly at COP-1.
• Non-standard case. FIR-A or FIR-B needs to change a condition (e.g. level capping for traffic in FIR-B, or descent to optimise arrival).
  • FIR-A side: OLDI CDN with the proposed new condition.
  • Gateway translates to ICAO AIDC CDN.
  • FIR-B replies with ICAO AIDC ACP (accept) or counter-CDN.
  • Gateway translates ACP back to OLDI COD.
  • FIR-A FDPS updates the trajectory; controllers are alerted on both sides.

Stage 5 — Transfer of Control#

• OLDI side. Transfer of control happens implicitly at COP-1 under LoA conditions; no dedicated OLDI message is required.
• ICAO AIDC side. FIR-A's gateway emits TOC as the flight approaches COP-1; FIR-B's FDPS replies with AOC when the receiving controller has assumed control.
• The gateway suppresses TOC/AOC towards the OLDI side because OLDI has no equivalent message; the LoA fixes the equivalent procedure.

Stage 6 — Transfer of Communication#

A few minutes before or after COP-1 (per LoA), FIR-A controller instructs the pilot to contact FIR-B on the new frequency.

• Where CPDLC is in use end to end, this is supported by data link handover; otherwise it is a voice instruction.
• The AIDC dialog itself does not normally carry a transfer-of- communication message.

Stage 7 — Revision (if any)#

If the flight is re-routed or re-cleared in FIR-A in a way that affects FIR-B (e.g. new level at COP-1, change of COP), FIR-A emits OLDI REV that the gateway translates to ICAO AIDC CDN (or amended CPL) for FIR-B.

Stage 8 — Abrogation (if needed)#

If the flight is cancelled, returns to departure, or diverts before crossing COP-1, FIR-A emits OLDI MAC. The gateway translates to ICAO AIDC MAC, with the semantic caveat that ICAO AIDC MAC has additional meaning around assumption of control. The LoA fixes how this semantic gap is handled (typically by also emitting a free-text INF or by AFTN telex).

Stage 9 — Civil-Military leg (if applicable)#

If COP-1 lies near restricted/reserved airspace managed by FIR-A's military authority, an OLDI XIN/XRQ/XAP dialog may run in parallel between FIR-A's civil ATC and the military AMC. There is no ICAO AIDC equivalent in the MID ICD; if FIR-B needs to know, it is informed by AFTN message or voice.

Stage 10 — Connection health#

Throughout, FMTP heartbeats and AIDC LAM acknowledgements keep both sides aware of link state. If the AIDC link drops, both sides revert to the AFTN/voice fallback procedure in the LoA, and the AIDC implementation indicator at the regional level is impacted.

Why this matters#

The point of AIDC is that all of Stages 2-9 happen in seconds without human intervention, leaving controllers free to focus on tactical separation and only on the non-standard cases. The point of OLDI/AIDC mapping at the EUR/MID seam is that the dialog still works when the two sides speak different message catalogues, provided the LoA and the gateway are correctly configured.

An enabler in this context is anything without which a regional AIDC implementation cannot deliver. Enablers fall into bearer infrastructure, procedural agreements, regulatory and standards basis, and institutional bodies that host the regional ICDs.

1. Bearer infrastructure#

AFTN (Aeronautical Fixed Telecommunication Network)#

The legacy character-oriented store-and-forward network defined in Annex 10 Volume II. AFTN is still the universal fallback for flight-plan and AIDC traffic in the MID Region and remains the ultimate backstop where the AIDC link is unavailable.

• Annex 10 Volume II Chapter 4 fixes message priorities, including the priority categorisation that AIDC inherits.
• AFTN addressing uses 8-letter location indicators.

AMHS (ATS Message Handling System)#

The X.400-based replacement for AFTN, defined in Doc 9880 (ATN/OSI) and Doc 9896 (ATN/IPS) provisions. AMHS is the EUR Region default for inter-centre messaging and is rolled out across the MID Region as part of the same modernisation as AIDC.

ATN (Aeronautical Telecommunication Network)#

The OSI-based ATN (Doc 9705) and the IP-based ATN/IPS (Doc 9896) provide the future bearer for AIDC. Doc 4444 §11 references AIDC priority categorisation on the ATN. ATN/IPS adoption in the MID is incremental and tied to PENS-equivalent regional connectivity.

FMTP (Flight Message Transfer Protocol)#

The EUR-specific TCP/IP peer-to-peer protocol that carries OLDI between adjacent FDPSs. Current specification is FMTP Edition 2.0. FMTP replaced legacy CIDIN/X.25 bearers and is mandated under EU interoperability rules.

Bilateral IP circuits#

Direct IP circuits between adjacent ANSPs are common on the MID Region and on EUR/MID seams where neither AMHS nor ATN/IPS is yet production. These are governed by the LoA and require security review under each State's policy.

2. Procedural enablers#

Letters of Agreement (LoA)#

The pivot of every AIDC pair. The LoA fixes:

• Standard coordination conditions (level band at each COP, route segments, climb/descent restrictions).
• Message subset in use (which OLDI / ICAO AIDC messages are actually exchanged on this seam).
• Response timers and silent-transfer rules.
• Loss-of-comms procedure and AFTN/voice fallback.
• COP register (named and bearing/distance COPs).
• Civil-military arrangements where applicable.
• Bearer endpoints (FMTP IP/port; AFTN/AMHS addresses).

Regional Supplementary Procedures (Doc 7030)#

Doc 7030 carries regional supplements for EUR and MID that supplement Doc 4444 with regionally agreed coordination procedures, phraseology, and message handling.

Annex 11 / Doc 4444 base obligations#

• Annex 11 Chapter 3 — coordination between ATS units.
• Annex 11 Chapter 6 — aeronautical fixed service obligations.
• Doc 4444 Chapter 10 — coordination procedures.
• Doc 4444 Chapter 11 — AIDC procedures and Appendix 6 message set.

3. Standards and avionics-side enablers#

Although AIDC is a ground-ground topic, parts of the operational chain depend on aircraft-side capability:

• CPDLC (FANS-1/A or ATN B1/B2) for end-to-end transfer of communication where data link is in use.
• PBN equipage (Doc 9613) so that COPs in Free Route Airspace are flyable and the trajectory matches what AIDC coordinates.
• Mode S Enhanced Surveillance so that AIDC's level information matches what surveillance reports.

These are not enablers of AIDC itself but of the operational use it supports.

4. Regulatory framework#

EUR#

• EU Single European Sky Implementing Regulations on flight-data interoperability mandate OLDI/FMTP between SES ANSPs.
• EASA ED Decision 2023/015/R reissues the OLDI Specification as Acceptable Means of Compliance.
• EUROCONTROL Guidelines for ATC Coordination and Transfer of Control (ED-2.0) consolidate the operational practice that LoAs reference.

MID#

• MIDANPIRG conclusions endorse the MID AIDC ICD and the AIDC/OLDI Priority 1 ANPI.
• State CAA approvals (operational authorisation, safety oversight under Annex 19 SMS).
• Cross-border IP connectivity security review under each State's national framework.

5. Institutional bodies#

EUR#

• EUROCONTROL — publishes and maintains the OLDI and FMTP specifications; runs the Network Manager; hosts the LSSIP cycle.
• EASA — issues AMC / GM and oversees compliance with SES IRs.
• SESAR JU / European ATM Master Plan — strategic context for OLDI evolution and successors (Flight Object, ED-133).

MID#

• ICAO MID Regional Office (Cairo) — secretariat for MIDANPIRG.
• MIDANPIRG ATM Sub-Group — owner of the MID AIDC ICD.
• MIDANPIRG CNS Sub-Group — owner of bearer infrastructure (AFTN/AMHS/ATN, MID PENS-equivalent).
• MID Air Navigation Report — annual implementation status.

Cross-region#

• ICAO Headquarters — Doc 4444 / Annex 11 / Annex 10 owner; curates regional coordination across MIDANPIRG, EANPG, APANPIRG.
• APAC Regional Office — owner of the APAC AIDC ICD with which the MID ICD is aligned but not identical.

How enablers are managed in practice#

Both regions track AIDC implementation as a performance indicator: EUROCONTROL through LSSIP, MIDANPIRG through the AIDC/OLDI Priority 1 ANPI and the annual MID Air Navigation Report. A state-pair is considered fully implemented only when bearer, LoA, message subset, training, and fallback are all in place — not just when the FMTP or AIDC link first comes up.

The performance lens for regional AIDC#

Regional AIDC is a means, not an end. It exists to lift performance on the KPAs Doc 9854 / Doc 9883 define for ATM. Both EUR and MID track AIDC as a performance indicator and tie it to broader performance objectives.

The chain:

KPA  --(measured by)-->  KPI  <--(targeted by)--  Performance Objective  --(achieved by)-->  AIDC implementation

Primary KPAs improved by EUR/MID AIDC#

• Interoperability — the headline KPA. Cross-border AIDC is the operational expression of interoperability between ATS units, and EUR/MID AIDC is the cross-region case.
• Safety — automated coordination reduces voice workload, mis- hearing risk, and missed coordination on busy seams.
• Capacity — predictable coordination supports denser sector loading and tighter level/route allocation.
• Predictability — pre-notification (ABI) and revision (REV/ CDN) keep the receiving unit aligned with the latest trajectory.
• Flight efficiency — CDN/COD negotiation can preserve user-preferred level/route across the boundary instead of forcing level capping.
• Cost-effectiveness — once deployed, AIDC reduces controller voice workload per flight.
• Global Interoperability — EUR/MID seam handling demonstrates whether the OLDI and ICAO AIDC realisations can interoperate at scale, which is a Doc 9854 ambition.

Performance Objectives relevant here#

Examples, consistent with EUROCONTROL Performance Review and MIDANPIRG ATM SG framing:

• PO — Implement AIDC/OLDI Priority 1 between identified ACC pairs. The MID Region ANPI; current MIDANPIRG target revised to end-2026.
• PO — Reduce reliance on voice coordination on cross-FIR boundaries. Measured by share of coordinated flights using AIDC vs. voice.
• PO — Improve predictability on cross-region seams. Measured by variance between estimated and actual boundary crossing time.
• PO — Preserve flight efficiency across boundaries. Measured by level-cap rate and re-route rate at boundary.
• PO — Reduce loss-of-coordination occurrences. Measured by reportable events involving missing or wrong coordination.

Key Performance Indicators#

Implementation KPIs#

• Percentage of identified ACC pairs with AIDC/OLDI operational (MID Region target: 70 percent originally end-2020, revised upward through end-2026; current regional average around 73 percent per the 2024 MID Air Navigation Report).
• Number of OLDI links operational under FMTP Edition 2.0 in the EUR Region (LSSIP reporting).
• Edition currency: percentage of OLDI links on the latest specification edition (5.1 in 2023).

Operational KPIs#

• AIDC message success rate (fraction of operational messages receiving a LAM within the LoA-defined timer).
• Coordination silent-transfer rate (fraction of flights crossing under standard LoA conditions without explicit CDN/COD).
• Level-cap occurrence rate at boundary (proxy for negotiated efficiency).

Safety KPIs#

• Loss-of-coordination events per million flights crossing the state-pair boundary.
• Reduction in voice frequency occupancy on coordination channels after AIDC deployment.

Predictability KPIs#

• Standard deviation between ABI estimate, ACT estimate, and actual boundary crossing time.
• Time between coordination message and operational effect.

Interoperability KPIs (EUR/MID seam specific)#

• Number of state-pairs operating dual-stack or gateway-mediated OLDI <-> ICAO AIDC links.
• Translation success rate on the gateway (fraction of operational messages crossing the gateway without manual fallback).
• Number of LoAs covering OLDI/AIDC translation explicitly.

How performance is reported#

EUR#

• EUROCONTROL Performance Review Body — annual reports, including coordination performance.
• LSSIP cycle — annual State-by-State input; covers OLDI and FMTP edition deployment.
• Network Manager Operational Performance Report — covers cross-border coordination indirectly through delay attribution.

MID#

• MIDANPIRG Air Navigation Report — annual, includes the AIDC/OLDI Priority 1 ANPI status table.
• MIDANPIRG ATM SG outcomes — biannual or annual; review the AIDC ICD and the implementation indicator.
• MIDANPIRG CNS SG outcomes — bearer-side reporting (AFTN/AMHS, ATN/IPS pilots).

Cross-region#

• The EUR/MID seam state-pairs are reported into both LSSIP (for the EUR side ANSPs) and the MID Air Navigation Report (for the MID side ANSPs). There is no consolidated cross-region report; the ICAO HQ side relies on regional inputs.

Why this matters for planning#

Tying AIDC deployment to KPAs and KPIs forces State-level decisions to be justified by measurable benefit, not by box-ticking against an implementation indicator. A State-pair that has AIDC "operational" but where 30 percent of flights still trigger voice-coordination fallback is not actually delivering the intended benefit, and that gap shows up in the operational and safety KPIs above.

Three timelines to keep distinct#

When discussing AIDC dates in EUR and MID, separate three things:

1. Specification / ICD edition timeline — when EUROCONTROL published OLDI/FMTP editions and when MIDANPIRG endorsed AIDC ICD versions.
2. Bearer evolution timeline — when CIDIN/X.25, AFTN, AMHS, ATN/IPS, and FMTP became available regionally.
3. State-pair implementation timeline — when individual ACC pairs activated AIDC/OLDI links operationally.

OLDI specification timeline (EUR)#

Intermediate edition dates between Edition 1 and Edition 5 vary in open sources; consult the EUROCONTROL specification register for the authoritative dates.

MID AIDC ICD timeline#

These figures are taken from MIDANPIRG papers via web search and should be reverified against the latest MIDANPIRG / RASG-MID report before quoting in formal work.

Bearer evolution#

1980s ----- 1990s ----- 2000s ----- 2010s ----- 2020s
  AFTN       CIDIN/X.25   FMTP 1.x   FMTP 2.0    FMTP 2.0 +
                          OLDI       OLDI 5      OLDI 5.1
                          (EUR)
                                      AMHS rollout (EUR/MID)
                                                  ATN/IPS pilots
                                                  (MID)

Throughout, AFTN remains the universal fallback. AMHS rollout in EUR is mature; in MID it is uneven across States. ATN/IPS pilots exist on selected MID and EUR/MID seams but are not yet the production bearer.

State-pair implementation milestones (indicative)#

The following are illustrative based on MIDANPIRG ATM SG outcomes and open MID Air Navigation Reports. Specific cutover dates and message-set scope are LoA-controlled and not reliably stated in open sources.

• UAE - Oman (Emirates FIR / Muscat). Early MID adopter; AIDC operational with iterative ICD refinement on high-density Gulf seam.
• UAE - Saudi (Emirates FIR / Jeddah). AIDC operational with Priority 1 status.
• Bahrain - Saudi (Bahrain FIR / Jeddah). Priority 1 implementation.
• Egypt - Saudi (Cairo / Jeddah, Red Sea). Priority 1 implementation.
• Cairo - Athens (EUR/MID seam). OLDI/FMTP on Athens side, AIDC on Cairo side; gateway operation.
• Cairo - Nicosia. Similar gateway pattern.
• Tehran - Ankara. OLDI/FMTP on Ankara side, AIDC on Tehran side where political/technical access permits.

Cross-region trials#

• EUR/MID gateway trials. Ad-hoc bilateral trials at Cairo- Athens, Cairo-Nicosia, and Tehran-Ankara seams to validate OLDI to ICAO AIDC translation. Results feed both LSSIP (EUR side) and MIDANPIRG (MID side).
• AMHS rollout. Underway across MID; reduces AFTN-only fallback pressure when AIDC is unavailable.
• ATN/IPS pilots. Limited; mostly tied to PENS-equivalent regional connectivity initiatives.
• Flight Object (EUROCAE ED-133) experiments. EUR experiments with SWIM-style flight-data sharing complementing OLDI; not yet a MID-side topic in production.

Where to find the latest dates#

Date assertions in this folder should be reverified against the following live sources before formal use:

• EUROCONTROL OLDI and FMTP specification registers.
• EASA ED Decision register.
• MIDANPIRG ATM SG and CNS SG outcomes (most recent meeting).
• MID Air Navigation Report (most recent edition).
• LSSIP State views (most recent annual cycle).

The dates above are illustrative as of 2024-2025 reporting and will shift as MIDANPIRG and EUROCONTROL publish new outcomes.

Primary ICAO documents#

• Annex 11 (Air Traffic Services), Chapter 3 — coordination between ATS units, including conditions of transfer of control and notification.
• Annex 11 (Air Traffic Services), Chapter 6, §6.2 — aeronautical fixed service, ground-ground communications between adjacent ATS units (basis for AIDC/OLDI requirement).
• Annex 10 (Aeronautical Telecommunications), Volume II, Chapter 4 — message priorities on the AFTN/ATN; AIDC priority categorisation on the ATN.
• Doc 4444 (PANS-ATM), Chapter 10 — coordination between ATS units (notification, coordination, transfer of control, transfer of communication).
• Doc 4444 (PANS-ATM), Chapter 11, §11.2.2.2 — ATS messages of Appendix 3 "shall be supplemented with, and/or replaced by" Appendix 6 AIDC messages on the basis of regional air navigation agreements.
• Doc 4444 (PANS-ATM), Chapter 11, §11.3.5.1 — AIDC addressing rule: sending unit identifies the receiving ATS unit and every message names the next ATS unit.
• Doc 4444 (PANS-ATM), Chapter 11, §§11.3.7.3, 11.3.7.5, 11.3.7.7 — AIDC notification, Coordinate Initial / Coordinate Negotiate, and Application Accept semantics.
• Doc 4444 (PANS-ATM), Appendix 6 — ATS Interfacility Data Communications (AIDC) message catalogue (LAM, ABI, CPL, EST, ACP, TOC, AOC, MAC, ...).
• Doc 7030 — Regional Supplementary Procedures — region-specific supplements (EUR, MID).
• Doc 9694 — Manual of Air Traffic Services Data Link Applications — operational use of AIDC messages (referenced from 4444 §11.2.2.2.1 Note).
• Doc 9705 — Manual of Technical Provisions for the Aeronautical Telecommunication Network (ATN) — ASN.1 PER encoding and AIDC addressing on the ATN.
• Doc 9804 — Manual on the Aeronautical Telecommunication Network (ATN) using ISO/OSI Standards and Protocols — regional ICD context for AIDC.
• Doc 9880 — Manual on Detailed Technical Specifications for the Aeronautical Telecommunication Network (ATN) using ISO/OSI Standards and Protocols — AMHS technical detail.
• Doc 9896 — Manual on the Aeronautical Telecommunication Network (ATN) using Internet Protocol Suite (IPS) Standards and Protocols — ATN/IPS basis for future AIDC bearer.

Regional ICDs and implementation references#

• ICAO MID Region AIDC ICD — regional profile of the ICAO AIDC message set for MID ACC pairs. Maintained under MIDANPIRG ATM Sub-Group (authoritative source — not in local library).
• ICAO Asia/Pacific AIDC ICD — APAC ICD, the de facto reference for the ICAO AIDC message subset; alignment basis for the MID ICD (authoritative source — not in local library).
• MIDANPIRG ATM SG/11 outcomes (2025) — current AIDC/OLDI Priority 1 implementation indicator status and revised target (authoritative source — not in local library).
• MIDANPIRG CNS SG/14 Report (2025) — bearer infrastructure context (authoritative source — not in local library).
• MID Air Navigation Report (2024) — annual implementation status (authoritative source — not in local library).

EUR specifications and regulatory basis#

• EUROCONTROL Specification for On-Line Data Interchange (OLDI), Edition 5.1, 2023 — European regional message set (ABI, ACT, REV, LAM, MAC, COD/CDN, XIN/XRQ/XAP) (authoritative source — not in local library).
• EUROCONTROL Specification for the Flight Message Transfer Protocol (FMTP), Edition 2.0 — TCP/IP peer-to-peer bearer for OLDI between adjacent FDPSs (authoritative source — not in local library).
• EASA ED Decision 2023/015/R — reissues the OLDI Specification as Acceptable Means of Compliance under SES interoperability rules (authoritative source — not in local library).
• EUROCONTROL Guidelines for ATC Coordination and Transfer of Control (ED-2.0) — operational guidance referenced by LoAs (authoritative source — not in local library).
• EUROCAE ED-133 — Flight Object Interoperability Specification (SWIM-style flight-data sharing complementing OLDI/AIDC) (authoritative source — not in local library).
• European ATM Master Plan — strategic context for OLDI evolution and successors (authoritative source — not in local library).
• LSSIP — Local Single Sky Implementation cycle — annual reporting against ICAO ASBU and the European ATM Master Plan (authoritative source — not in local library).

Live URLs#

• EUROCONTROL Specification for OLDI (Edition 5.1, 2023): https://www.eurocontrol.int/sites/default/files/2023-06/eurocontrol-oldi-specification-5-1.pdf
• EUROCONTROL Specification for FMTP, Edition 2.0: https://www.eurocontrol.int/publication/eurocontrol-specification-interoperability-and-performance-requirements-flight-message
• EASA ED Decision 2023/015/R (OLDI as AMC): https://www.easa.europa.eu/en/downloads/138749/en
• EUROCONTROL Guidelines for ATC Coordination and Transfer of Control (ED-2.0): https://www.eurocontrol.int/sites/default/files/2023-07/guidelines_for_atc_coordination_and_transfer_of_control_ed-2-0.pdf
• ICAO MIDANPIRG portal: https://www.icao.int/MID/Pages/Midanpirg.aspx
• MIDANPIRG CNS SG/14 Report (2025): https://www.icao.int/sites/default/files/MID/MeetingDocs/2025/Fourteenth%20Meeting%20of%20the%20of%20the%20MIDANPIRG%20Communication,%20Navigation%20and%20Surveillance%20Sub-Group%20(CNS%20SG/6-%20Report/CNS-SG14-Report.pdf
• MID ATM SG/11 IP02 (2025, AIDC/OLDI implementation): https://www.icao.int/sites/default/files/MID/MeetingDocs/2025/Eleventh%20Meeting%20of%20the%20MIDANPIRG%20Air%20Tarffic%20Management%20Sub-Group/2-%20Documentation/IP02.pdf
• MID Air Navigation Report 2024: https://www.icao.int/sites/default/files/MID/Documents/MID-AN-Report-2024-Final.pdf
• ICAO GANP Portal: https://ganpportal.icao.int/

ICAO Annexes most touched#

• Annex 1 (Personnel Licensing) — controller licensing for AIDC operations.
• Annex 10 (Aeronautical Telecommunications), Volumes II, III — AFTN, AMHS, ATN.
• Annex 11 (Air Traffic Services) — coordination obligations.
• Annex 19 (Safety Management) — SMS over the AIDC operation.

Validation note#

Implementation status figures and target dates above are taken from MIDANPIRG papers and EUROCONTROL specification records via web search. Reverify against the latest MIDANPIRG / RASG-MID and EUROCONTROL / EASA publications before quoting in formal work.