Local A-CDM Procedure

Since November 3rd, 2010, Airport-CDM is mandatory procedure for all process partners involved at Frankfurt Airport.
This section contains:

  • General overview of the A-CDM procedure
  • All necessary information to take part in the A-CDM procedure at Frankfurt Airport:
What is Airport CDM ?

Airport Collaborative Decision Making (A-CDM) is an European initiative based on operational harmonisation (EUROCONTROL), technical standardisation (EUROCAE) and mandate of the  European Commission (Community Specification). Airport CDM is an operational process which aims at improving Air Traffic Flow and Capacity Management (ATFCM) at airports by reducing delays, improving the punctuality of events and optimising the utilisation of resources. It allows an airport partner to make the right decisions in collaboration with other airport partners (the airport operator, aircraft operators, ground handlers, the air navigation service provider, the Network Manager Operations Centre – NMOC, support services), knowing their preferences and constraints in regard to the actual and predicted situation.The decision making of the airport partners is facilitated by sharing accurate and timely information and by adapting procedures, mechanisms and tools.The Airport CDM procedure comprises the time period from Estimated Off Block Time (EOBT) -3hr untill Take Off-, until the completion of the turn-round process, while considering all sixteen existing milestones.

Expected benefits to partners of Airport CDM

All airport partners will benefit from Aiport CDM:

  • Aircraft operators: better adherence to schedule, possibility to express preferences,  more dynamic adjustment of ATC-Slots
  • Ground handlers: improved predictability of turnround operations, better useage of resourcesAirport operator: increased departure and arrival punctuality, more efficient use of stands, gates and terminals
  • ATC: optimised use of airport airside infrastructure, reduced ground congestions
  • NMOC: better adherence to slots, optimised use of airspace capacity
A-CDM in Frankfurt

In April 2008, Fraport AG and DFS initiated an Airport CDM project at Frankfurt Airport. The Project aimed to develop the A-CDM procedure for Frankfurt based on European standards, necessary system adaptations and adopting A-CDM into a regular operation.

After an intensive working phase the Airport CDM process has been successfully and on time put into regular operations at Frankfurt Airport in February 2011. Frankfurt isthe fourth airport after Munich, Brussels, Paris CDG, to implement the A-CDM  procedure completely including the data link to the network management
unit in Brussels and the six A-CDM concept elements.

The implementation of Airport CDM improves the airside processes and utilizes slots more efficiently. This is reflected in a greater outbound punctuality and an improved utilization of resources for all partners involved.

The Airport CDM implementation project was finished at the end of 2011. Since that time the A-CDM responsibilities and support have been integrated into line organization of Fraport and DFS-Tower FRA.

Airport CDM@FRA team

Representatives of the following partners participate in the Airport CDM team:

  • DFS (Tower)
  • Fraport (Aviation Airside and IT-Services)To view the contact information please click here.

Airport CDM is the concept which aims at improving operational efficiency at airports by reducing delays, improving the predictability of events during the progress of a flight and optimising the utilisation of resources.

With Airport CDM the network is served also with more accurate take-off information to derive ATFM slots. As more airports implement Airport CDM, the network will be able to utilise available slots more efficiently and reduce the current buffer capacity.

The improved decision making by the Airport CDM Partners is therefore facilitated through sharing accurate and timely information and by adapted operational procedures, automatic processes and easy to use tools. The EUROCONTROL Airport CDM team is responsible to ensure standardization and distribution of best
practice methods for implementation of Airport CDM at European airports. The concept is an integral part of the SESAR program.

The common goals of Airport CDM are as summarised in the diagram below:

Airport CDM Generic Processes are highly recommended for implementation of the milestones-approach-concept, as described in the Eurocontrol Implementation Manual. It describes milestone events itself, as well as actions where some Milestones do not occur at the intended/scheduledmoment. The described processes are automated and used to inform Airport CDM partners of inconsistencies in provided information as well as updated predictions of target off block, start up approval and take-off times.The milestone processes are also linked to the Departure Planning Information (DPI) messages which will supply the NMOC with reliable data concerning the progress of the flight. The outputs of the milestone processes are alert messages to airport partners and DPI messages to NMOC. Whereas the milestones mark a special event, the process may also be activated when this event does not occur at the scheduled time.



Airport CDM is an operational concept built of elements aiming to achieve greater operational efficiency. It is implemented in the airport environment through the introduction of operational procedures and automated processes which realise the aims of the concept elements.

A phased, bottom-up approach for implementation of the concept elements is essential, in order to achieve maximal benefits.

Of the available Airport CDM concept elements, Information Sharing is essential because it creates the foundation by enabling the sharing of information and creating a common situational awareness. In addition, it potentially adds predictability and resource efficiency benefits. After creating this information platform, the main priority is to implement the TOBT by using the Milestone Approach, to improve predictability during the turn-round process of aircrafts. These two are essential requirements for the implementation of the remaining concept elements. With variable Taxi Time in place, the link between off-block time and take off time becomes transparent to all partners and NMOC, and a proper prediction of the take off time can be communicated towards the network function represented by NMOC. With the pre-departure sequencing function the TSAT can be calculated, providing an off block sequence. With the above four elements in place, the last local airport step is to implement CDM in Adverse Conditions. Using pre-departure sequencing in situations where different bottlenecks occur, enables Air Traffic Control to keep the traffic capacity maximally utilized. With all local Airport CDM concept elements successfully implemented, the airport is ready to connect with the NMOC for Collaborative Management of Flight Updates with the exchange of FUM and DPI messages.



All milestones together constitute the Airport CDM procedure and are basis for the process description, publications and the necessary system adjustments.



TOBT (Target Off-Block Time)

Definition:  The TOBT is a point in time to be monitored and confirmed by the airline/handling agent at which the ground handling process is concluded, all aircraft doors are closed, all passenger boarding bridges have been removed from the aircraft and thus start-up approval and push-back/taxi clearance can be received.

All ground handling processes, except push-back and de-icing, are based on the TOBT.

TOBT = forecast of "Aircraft ready"


Who sets the TOBT?

The person responsible for TOBT (as defined by Aircraft Operator, e.g. handling agent)

What has to be done?

Management of TOBT (entry, update and if necessary deletion)

When does it have to be done?

The earliest time to enter the TOBT is 90 minutes prior to EOBT. Prerequisite: The Flight Plan data coherency check (Milestone no.1) was executed successfully.

  • A TOBT has to be available for all flights
  • After the linked inbound flight has taken off from the previous airport ("Take Off from Outstation"), a TOBT is generated automatically for the outbound flight
  • The earliest time for the generation and publication of a TOBT is: EOBT -90 minutes
  • A manually set TOBT will never be overwritten by an automatically generated TOBT
  • The TOBT shall not be earlier than the EOBT - 10 minutes
  • If the TOBT cannot be kept it has to be updated or deleted
  • The updated TOBT has to differ by +/- 5 minutes from the previous one
  • The TOBT may be changed as often as needed until the publication of the TSAT. After this it may be changed up to three times, thereafter it has to be deleted and a new TOBT may be entered

The Sequence Planner at Frankfurt Airport automatically calculates   flexible and steady start-up sequences to support a coordinated off-block process. The system has been developed by ATRiCS based on Fraport AG requirements and is fully compliant with the European Community Specification for A-CDM and the national initiative “German   Harmonization of Airport CDM“. In particular, it fully meets the  requirements for Collaborative Pre-Departure Sequencing (Airport CDM Functional Group 5).

Our Pre-Departure Sequence Planner balances the departure demand with the available runway capacity. In case of a predicted over-demand at the runway, the traffic flow is automatically regulated by generating segregated Target Start-Up Approval Times (TSAT), thereby taking into account:

  • Runway capacity
  • Air traffic flow management constraints (CTOTs)
  • Scheduled departure times
  • Taxi times
  • Target off block times
  • Position conflicts
  • Tower freeze
  • De-icing times


The A-CDM Concept Element ‘Information Sharing’ is the foundation of the A-CDM procedure. It enables the sharing of information and creates a common situational awareness. Information Sharing also enhances the
decision making process, because it allows all partners to act based on the shared information. Thus actions can be taken to optimize airside processes as well as the allocation of recourses (infrastructure, equipment, or staff). Information sharing also has a network effect. It leads to a better management of the airspace capacity by ATC and the
network manager.

Airport CDM Alerts
  • are an essencial part of the Aiport CDM procedure
  • inform all partners about possible problems ahead of time
  • enable smooth operations in case the alerts are paid attention to

Within the process alerting messages are initiated by:

  • Local events and plausibility checks
  • Error / Warning messages during data exchange with NMOC

The display of the alerting messages within the systems will let you know whether:

  A-CDM process for a flight will immediately be stopped or interrupted
The process continues, but the existing conflict has to be solved or
If they are warning messages and get ignored, it will lead to consequences at a later time.
Euro CDM Alerts
No Airport Slot available, or Slot already correlated
SOBT vs. EOBT discrepancy
Aircraft Type discrepancy
Aircraft Registration discrepancy
Destination discrepancy
CDM06 Non-Airborne Alert (is not used)
CDM07 EIBT + MTTT discrepancy with EOBT
CDM07a EIBT + MTTT discrepancy with TOBT
CDM08 EOBT Compliance Alert
CDM09 Boarding Not Started
CDM10 TOBT Rejected or Deleted
CDM11 Flight not compliant with TOBT / TSAT
CDM12 TSAT Not Respected by ATC (is not used)
CDM13 No ATC Flight Plan Available
CDM14 Automatic TOBT Generation not possibles (is not used)
CDM17 TTOT within night flying restriction    
CDM34 Return to Stand notification
CDM40 Flight not compliant with TOBT for deicing
CDM43 Deicing cancelled and TOBT deleted

Reporting channels for alerting messages to AO/GH will be:

A-CDM Alerts and alert numbers are harmonised on European level.



Providing network operations with precise Target Takeoff Times (TTOT) and all changes will ensure the continued accuracy of the network traffic prediction for A-CDM Airports.

By establishing Airport CDM information exchange with the Network Operations systems, Collaborative Management of Flight Updates is re-conciliating the network view with
Airport operations, closing the loop between en route / arrival constraints and departure planning.

In Collaborative Management of Flight Updates the exchange of information between the Network Operations and the airport is realised by:

  • Sending Departure Planning Information Messages (DPI) from the airport to the Network Operations concerned
  • Sending Flight Update Messages(FUM) from the Network Operations to the airports concerned

Collaborative Management of Flight Updates will bring significant benefits in term of network management and Aircraft Operators and Airports management of resources. It will not only improve the accuracy of the flight information before departure, leading to better efficiency of the ATFCM activity, but it will also open the door to a more collaborative approach to traffic management between the network level
and local operations.

The implementation of Airport CDM improves the airside processes and utilizes slots more efficiently. This is reflected in a higher outbound punctuality and an improved utilization of resources for all partners involved.

Summarized the measured outcomes of Airport CDM are:

  • Significantly improved prediction and accuracy of TOBT provided by the aircraft operators.
  • Increased efficiency and stability of all TOBT related operational processes affecting a significantly improved outbound punctuality.
  • Improved runway usage and runway take-off flow.
  • Reduction of the impact of delayed arrival on the punctuality of the subsequent departure.
  • Improved utilization of aircraft stands and gates.
  • Improved CTOT adherence.
  • Reduction of ATFM delay due to better CTOT allocation as a result of the DPI exchange with NMOC.
Development of Performance Figures
On time Outbound
Stability Aircraft Stand Allocation/Planning
Target Off-Block Time (TOBT)-Quality II
New: Deviation TSAT-TOBT
New: average number of TSAT per flight
Taxi-in Time (AXIT)
Taxi-out Time (AXOT)
Process Time Outbound
New: Target Take-Off Time-Quality
DFS Take-off Quality
German A-CDM Harmonization


There are five German A-CDM airports (MUC, FRA, DUS, SXF and STR) with A-CDM fully implemented as well as one German A-CDM project (HAM). This makes it necessary to harmonize German A-CDM activities and subjects.

A-CDM@FRA is an active partner in the 'German A-CDM Harmonization' initiative which has the following objectives:

  • Exchange of information and best practices between the different German A-CDM airports (regardless if fully implemented or project)
  • Achievement of a common understanding of Airport CDM in Germany and representation of this understanding to the European A-CDM Harmonization Taskforce
  • Harmonization of the use and consequences of several A-CDM aspects -> “one face to the customer”