Estimated off-block time update service

Streamlining tactical flight operations using A-CDM data.

Any change of more than 15 minutes to the estimated off-block time (EOBT) of a filed flight plan has to be communicated to the EUROCONTROL Network Manager’s integrated flight plan filing system (IFPS). At collaborative decision-making (A-CDM) airports, the target off-block time (TOBT) values reflect any delays that can be attributed to the aircraft operator (AO) or to the ground handling operations.

EUROCONTROL as Network Manager is informed about the TOBT values via departure planning information (DPI) messages, disseminates and highlights these values to stakeholders, to ensure that they can be easily identified and solved. Aircraft operators have to react to a discrepancy by filing a delay (DLA) message based on the TOBT value.

To address this, at EUROCONTROL we provide a service to: 

  • automatically solve the EOBT – TOBT discrepancies, depending on the AO preferences;
  • reduce workload for the partners involved;
  • prevent last minute flight disturbances caused by misalignment of EOBT with TOBT.
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Supporting airports

In practice

Aircraft operators can delegate to EUROCONTROL NM the filing of DLA messages for departures from designated A-CDM airports. For flights operated by an AO that has delegated the DLA-filing, NM will automatically file a DLA message using the TOBT values in the DPI messages received.

Our IFPS will process and distribute this DLA message in the same manner as if the request was received from the AO directly. In addition, operational reply messages (ORM), containing the comment “This DLA message has been triggered from a DPI message”, are sent by IFPS to inform the AOCC and/or the FPL originator. An action from the AO is expected upon receiving an ORM of type REJ.

The aircraft operator is derived from the field 18 (OPR) of the FPL if it is filled in. Otherwise, it is derived from the call sign.

Discrepancy trigger

At the activation of the service the EOBT – TOBT discrepancy parameter value needs to be specified. The default value is 15 min. This means that every TOBT value received by NM, which exceeds the EOBT by more than 15 min, triggers a DLA message. However, a different parameter value (e.g. 10 min) may be recommended for certain A-CDM airports.

A TOBT which is earlier than the EOBT will not trigger an update of the EOBT. If the AO needs to advance the EOBT by more than 15 min the required action is to CNL and re-file, similar to the current procedure.

AOs using the EOBT Update service also have the option to choose between immediate or deferred transmission of the DLA.


TOBT values are normally made available to us at target start-up approval issue time (TSAT), which is around 30-40 min before TOBT. After this timeframe, the TOBT is considered confirmed and reliable. Therefore, the earliest automatic update of the EOBT can be expected in this period.

The aircraft operator, for which this service was activated at an A-CDM airport, will still be able to file delay, or change (DLA/CHG) messages on their own, if necessary.

Before the first DPI message is received (normally three hours prior to EOBT), we recommend that the staff at the aircraft operator control centre (AOCC) monitor and inform EUROCONTROL NM of any expected delay. Any DLA/CHG message is used to update the flight profile. Keeping us up-to-date will allow to provide a more accurate picture of the capacity demand in the network.

The update of the EOBT with the TOBT value from a DPI message normally will not impact the network assessment because the EOBT is simply being aligned to a previously received TOBT.

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If you are interested in our service but have no previous experience with it, we recommend starting with a trial period during which the service would be activated for a limited number of airports (based on the three-letter ICAO code of the AO). For any questions, do not hesitate to contact us at Airport CDM: [email protected].