A-CDM and TOBT for ground handlers: keeping the ground's promise

A-CDM has changed the ground handler’s place in the airport. Departure time used to be a matter for the airline and air traffic control; today, at airports that have implemented it, one key time comes from the ground: the TOBT. For a ground handler, A-CDM and the TOBT are not just another administrative task. An accurate TOBT lets the tower build a realistic departure sequence; a wrong one disrupts that sequence for everyone.

This article takes the definitions and milestones from the Airport CDM Implementation Manual published by EUROCONTROL (version 5.0) and turns them into practical guidance for station teams.

A-CDM in brief

According to EUROCONTROL, A-CDM (Airport Collaborative Decision Making) aims to improve the efficiency and resilience of airport operations by optimising the use of resources and improving the predictability of air traffic. The partners are the airport operator, aircraft operators, ground handlers and air traffic control, working with the European Network Manager. The focus is on aircraft turnaround and pre-departure processes. EUROCONTROL states that A-CDM is fully implemented at 35 airports across Europe.

The manual describes six concept elements: information sharing, the milestone approach, variable taxi time, pre-departure sequencing, adverse conditions, and collaborative management of flight updates with the network.

The TOBT: a precise definition

EUROCONTROL’s manual defines the TOBT (Target Off-Block Time) as the time at which an aircraft operator or ground handler estimates the aircraft will be ready: all doors closed, boarding bridge removed, pushback vehicle available, and ready to start up or push back immediately upon receiving clearance from the tower.

Every word matters. “Ready” does not mean “boarding complete” or “holds being closed”. A TOBT declared while the tug is not on stand is not a TOBT that has been met.

Who is responsible for it?

The manual is clear: by default, the aircraft operator is responsible for the TOBT, but it may delegate part or all of that responsibility to its ground handler, because the handler is best placed to know the flight’s status once the aircraft is in-blocks. The final decision to delay a flight always remains with the airline. Local procedures at each airport specify who enters and updates the TOBT: check those at the airports where you operate and what your contract with each airline says.

The milestones that matter to the handler

EUROCONTROL’s manual tracks a flight through sixteen milestones:

The handler feeds several of these milestones directly. Milestone 8 (ground handling starts) mainly concerns the first flight of the day or an aircraft parked for a long time; for a normal turnaround, the manual treats ground handling as starting at AIBT. At that point, it says, the TOBT is updated automatically or manually by the airline or its ground handler, based on the estimated turnaround time.

Milestone 9 has special status: it is when the airline or ground handler provides its most accurate TOBT, at a locally agreed time, because air traffic control builds the pushback sequence on it. Milestone 11 (boarding starts, gate open and passengers physically boarding) gives, according to the manual, a good indication of whether the TOBT and TSAT will be met. Milestone 12 (aircraft ready) is provided by the airline or its ground handler.

The TSAT: what the tower does with the TOBT

According to the manual, the TSAT (Target Start-up Approval Time) is the time provided by air traffic control, taking into account the TOBT, any CTOT slot and the traffic situation, at which an aircraft can expect start-up or pushback approval. The TSAT is equal to or later than the TOBT. It is issued at a locally defined time.

The TOBT is the input; the TSAT is the output. If the TOBT is wrong, so is the TSAT, and with it the aircraft’s place in the sequence.

When the TOBT is missed

The manual sets out several alert and control mechanisms:

• TOBT passed without the aircraft ready: once the TOBT plus a local tolerance has passed with no ready status, the airline and ground handler are informed.
• No start-up request within the TSAT window: if the crew has not requested start-up by the end of the TSAT tolerance window, the airline and ground handler are informed and should update the TOBT.
• Too many updates after TSAT: the number of TOBT changes after TSAT issue is monitored; above a local threshold, the TOBT input is handled according to local procedure.

The consequences go beyond the flight concerned. The manual stresses that a non-reported delay can wreak havoc with the sequence, affect other flights, cause induced delays, lower runway throughput and tie up resources for longer than planned. It also notes that, under current flight plan procedures, the airline must update the EOBT in its flight plan when the TOBT differs from it by more than 15 minutes.

Finally, the split of responsibilities is clear: the airline or ground handler must make sure the aircraft is ready for start-up in line with the declared TOBT and TSAT; after start-up, air traffic control is responsible for the flight meeting its CTOT.

Good practice for ground handlers

One TOBT owner per flight

The TOBT needs a named owner, usually the turnaround coordinator. Regulation (EU) 2025/20, applicable from 27 March 2028, requires ground handling organisations to establish a turnaround coordination function; it is the natural owner of the TOBT when the airline has delegated it.

Update early rather than often

A TOBT updated as soon as a deviation is known gives the tower time to rework the sequence. A TOBT changed repeatedly after TSAT issue is exactly what the manual monitors. Good practice is to confirm a realistic TOBT at milestone 9 and only change it when something real happens.

Work from actual progress

A reliable TOBT is built on what is happening on stand: did the aircraft arrive on time, have the holds been offloaded, has cleaning started, is outbound baggage ready? Milestone 11 (boarding starts) is a useful marker: boarding that starts late makes a met TOBT unlikely.

Plan for adverse conditions

For adverse conditions (bad weather, de-icing, reduced capacity), the manual recommends that ground handlers build an extra buffer into TOBT predictions when operations cannot run as fast as normal, and adjust their TOBTs in line with revised arrival estimates.

Define “ready” for everyone

The TOBT includes the tug being available and the bridge removed. That equipment often depends on other teams or other providers. The rules for making it available must be known to all, and pushback resources tracked as a critical resource.

Measure and debrief

The manual suggests comparing TOBT and TSAT with the actual off-block time (AOBT) to measure their accuracy. Tracking this by wave and by turnaround type shows where TOBTs are optimistic and why. Recurring gaps usually point to organisation (resources shared between two flights, boarding started too late) rather than incidents. Our article on reducing handling-related delays covers these levers.

Agree the rules locally

Who bears the delay of an aircraft held on stand because its TSAT is later than its TOBT? The manual leaves this to local service level agreements. Better to have settled it in the SLA before the first dispute.

How Turnpilot helps

Turnpilot gives the turnaround coordinator a view of the actual progress of every turnaround, which helps confirm and update the TOBT in time; the decision stays with a person. The platform exchanges data with the airport’s A-CDM without replacing existing systems. The turnaround control module shows the station’s flights sorted by risk to departure time. For airport operators, the airports page explains how better-informed TOBTs help free stands on time.