A-CDM

Airport Collaborative Decision Making — for crews and dispatchers

v2 · 29/09/2026

What A-CDM is

Airport Collaborative Decision Making (A-CDM) is a set of procedures and data sharing between the aircraft operator, ground handler, airport operator, ATC and the Network Manager (NM). Everyone works from the same live times for each flight, so the turnaround, the start-up sequence and the ATFM slot are all planned on one shared picture.

The key idea is simple: the operator tells the system when the aircraft will really be ready (TOBT); ATC turns that into a start-up time (TSAT) that fits the runway sequence and any CTOT; the airport sends the resulting take-off estimate to the Network Manager through DPI messages, which improves the whole network's traffic prediction.

In Europe the reference documents are the EUROCONTROL Specification for A-CDM (Ed. 1.0, Jan 2025 — successor of the A-CDM Implementation Manual v5, 2017) and the NM DPI Implementation Guide. Each airport publishes its own local rules (AIP AD 2.20/2.22 and an A-CDM brochure) — local rules always prevail over the generic values in this app.

Who does what

PartnerOwns / provides
AO Aircraft operatorFlight plan (EOBT), TOBT (may delegate it to the ground handler), de-icing request, crew/pax readiness.
GH Ground handler / FBOTurnaround progress; very often the TOBT responsible person on behalf of the AO (usual case for business aviation).
AP Airport operatorStand/gate allocation, the A-CDM platform, airport slot (SOBT) at coordinated airports, MTTT, taxi-time tables.
ATC Tower / pre-departure sequencerTSAT and the start-up/push sequence, taxi times (EXOT), start-up and push clearances.
NM Network ManagerCTOT for regulated flights; receives DPI messages from the airport, updates the flight's profile and can refine the slot.

The five building blocks

  1. Information sharing — one common platform with all times per flight.
  2. Milestone approach — 16 events (plus 3 de-icing events) that track the flight from flight-plan activation to take-off. See the Milestones tab.
  3. Variable taxi time — realistic EXOT/EXIT per stand and runway, not a single default.
  4. Pre-departure sequencing — TSAT issued from TOBT, taxi time, CTOT and runway capacity (first-come-first-ready, not first-come-first-served).
  5. Adverse conditions & collaborative management of flight updates — de-icing, capacity drops, and the DPI link to the Network Manager.

The chain in one line

EOBT (FPL) → TOBT (AO/GH) → TSAT (ATC) → +EXOT → TTOT (→ NM via DPI) ⇄ CTOT (NM)

  • TOBT = when the aircraft will be ready: doors closed, bridge/stairs removed, tug connected, ready for start-up/push immediately on clearance.
  • TSAT = when you can expect start-up/push approval. It is never earlier than TOBT.
  • TTOT = the resulting take-off time (TOBT or TSAT + taxi-out time). If the flight has a CTOT, the sequencer places TTOT inside the slot window (−5/+10 min).

Why it matters to a bizjet crew

  • At an A-CDM airport your start-up is by TSAT, not by when you call. Calling early does not move you up.
  • A TOBT that is wrong (too early or not updated) costs you: missed TSAT → TOBT/TSAT deleted → you go back in the queue.
  • Your TOBT feeds the NM: a realistic TOBT can get you a better CTOT; an unrealistic one can lose you the slot.
  • At many CDM airports a TOBT more than 15 min after EOBT generates an automatic DLA — but the operator still owns the flight plan.

The 16 milestones

Each milestone is an event whose time is recorded in the A-CDM platform. Missing or late milestones trigger alerts and recalculations. Tap a milestone for details.

Source: EUROCONTROL Specification for A-CDM Ed. 1.0 (2025). Times such as TOBT+10 or TSAT±5 are the generic values; each airport may use its own.

Time parameters

Letters: Scheduled · Estimated · Target · Calculated · Actual. Tap a filter or search.

Key formulas

FormulaMeaning
EIBT = ELDT + EXITInbound: expected in-block from landing estimate plus taxi-in.
TOBT = EIBT + MTTTAutomatic TOBT before arrival (turnaround flights); the TOBT responsible person then confirms or updates it.
TOBT = AIBT + MTTTSame, once the aircraft is actually on blocks.
TTOT = TOBT + EXOTTarget take-off before sequencing.
TTOT ≈ TSAT + EXOTOnce sequenced, the take-off target follows the start-up time (TSAT ≥ TOBT).
TTOT = AOBT + EXOTAfter off-block, recalculated from the actual push time.
TTOT = ECZT + EDIT + EXOTWith de-icing: start of de-icing + de-icing duration + taxi (remote pad case).
CTOT −5 / +10ATFM slot tolerance window that the take-off must meet (for ATC).

DPI messages (airport → Network Manager)

MessageSent whenWhat it tells NM
P-DPIPredicted — flight plan received early (before EOBT −3 h)Early prediction of the departure.
E-DPIEarly — MST1 (FPL activated / correlated, ~EOBT −3 h)Flight known to the airport; first TTOT with taxi time.
T-DPI-tTarget — from MST2 (EOBT −2 h); each TOBT update or TTOT change ≥ 5 minTOBT-based TTOT; NM uses it to update the flight and the CTOT.
T-DPI-sSequenced — from TSAT issue (MST10); last one at start-up approval (MST14)TSAT-based TTOT — the most reliable take-off estimate.
A-DPIActual — at off-block (MST15)Aircraft has left the stand; the CTOT is frozen.
C-DPICancel — TOBT deleted, TSAT expired, return to stand, etc.Previous DPI info is no longer valid; the flight falls back to FPL data.

NM plans to end AFTN exchange for DPI: from 31/12/2027 B2B will be the only channel (Spec. A-CDM Ed. 1.0).

Main alerts you may hear about

AlertTrigger
CDM01No airport slot available, or slot already correlated (flight plan vs slot).
CDM02SOBT vs initial EOBT discrepancy.
CDM07Turnaround not feasible — EIBT + MTTT later than the EOBT.
CDM08EOBT/TOBT discrepancy — they differ by 15 min or more.
CDM10Off-block not recorded by ASAT + 5 min.

Alerts 50 and above are reserved for local use.

1 · Before the day

  • Check if the airport is A-CDM (AIP AD 2.20/2.22, airport A-CDM brochure, handler). Note the local values: TOBT update threshold, start-up window, push time after approval, how DCL is obtained.
  • File a realistic EOBT. The TOBT will be compared with it all day.
  • Agree with the handler/FBO who is the TOBT responsible person and how the crew passes updates (phone, app, portal). In business aviation this is usually the handler.
  • Remote stand or tow required? Build it into the TOBT — TOBT means ready to push/start at that time.

2 · Setting the TOBT

  • TOBT = all doors closed, stairs/bridge removed, tug connected (if needed), crew ready to start immediately.
  • It is not "pax arrival time" nor "engine start time + 10".
  • Give the handler an honest TOBT as early as you can; accuracy is what the sequencer needs.
  • The platform alerts (CDM08) when TOBT and EOBT differ by 15 min or more.

3 · Updating the TOBT

  • Update as soon as you know the change — typically when it changes by 5 min or more (local threshold may differ).
  • Best before the TSAT is issued (TOBT −40 to −30 min). A change after that re-sequences you — usually later.
  • Not ready at TOBT? Update it. If no update and no "ready" by TOBT +10, the TOBT is removed and you have no sequence.
  • Ready earlier? An earlier TOBT can give an earlier TSAT — and, via DPI, possibly a better CTOT.

4 · On frequency

  • Obtain the departure clearance (DCL/voice) as locally required, usually before the start-up request.
  • Request start-up within the TSAT window (commonly TSAT ±5 min). Calling earlier does not move you up.
  • After start-up approval, push/start promptly — many airports expect off-block within ~5 min (CDM10 alert at ASAT +5).
  • If you have not requested start-up by TSAT +10, TSAT and TOBT are removed → new TOBT via handler → new TSAT.

5 · TSAT and the CTOT

  • For a regulated flight, the sequencer sets the TSAT so the TTOT falls inside the CTOT window (−5/+10).
  • The T-DPI messages give NM your TOBT-based take-off time — NM can improve the CTOT when you are ready earlier, or re-issue it when you will be later.
  • If TOBT + EXOT is already after CTOT +10, the slot cannot be met — expect a new CTOT (the AO/handler can also send a DLA or ask NM for a slot change).
  • At off-block the A-DPI freezes the CTOT.

6 · EOBT, DLA and the flight plan

  • The AO remains responsible for the flight plan.
  • At airports covered by NM's EOBT Update Service, a TOBT later than EOBT by more than 15 min makes NM send a DLA automatically (for AOs using the service). Elsewhere, send the DLA yourself.
  • A DLA can only delay. To bring the EOBT earlier, the flight plan normally has to be cancelled and refiled.
  • IFPS/ICAO: a flight should not depart more than 15 min before, or later than 15 min after, its EOBT without a flight plan update.

7 · De-icing

  • Request de-icing as early as possible, through the handler or ATC as locally required (MST D1).
  • The platform adds the de-icing time: TTOT = ECZT + EDIT + EXOT (remote pad) — your TSAT may change.
  • On-stand and remote de-icing are handled differently — check whether the local TOBT includes the de-icing or not.
  • D2/D3 record start/end of de-icing (ACZT/AEZT); holdover time runs from the start of the final step.

8 · Quick turn at a CDM airport

  1. Arrival: handler confirms TOBT (from AIBT + MTTT or your estimate).
  2. Watch the clock at TOBT −40: TSAT will appear (handler/app/DCL).
  3. Change ≥ 5 min? → handler updates TOBT now.
  4. DCL, doors closed, tug ready by TOBT.
  5. Call start-up inside TSAT ±5.
  6. Push promptly after approval.
Generic values from the EUROCONTROL A-CDM Specification and typical airport briefings. Always check the airport's AIP and A-CDM brochure — windows (±5, TOBT +10, etc.), who enters the TOBT and how start-up is requested vary.

Timeline calculator

Enter times in UTC (HHMM). The sequencer delay simulates runway/stand queue. Leave CTOT blank for an unregulated flight.

Simplified model: TSAT = latest of TOBT + sequencer delay and (CTOT − EXOT − EDIT); TTOT = TSAT + EDIT + EXOT. Real sequencers also use stand, runway and local constraints.

Step through the departure

Uses the times above. Tap Next to move the clock milestone by milestone.

    Quiz

    A-CDM · study aid only — not an operational document. Based on the EUROCONTROL Specification for A-CDM Ed. 1.0 (2025), NM DPI Implementation Guide and published airport A-CDM briefings. Local procedures prevail.
    LR Aviation · lraviation.com.br