Tools Used for Traffic Flow Management

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Adaptive Compression

Adaptive compression is a new approach being used to help ensure that all slots in a program (TMI) are used.

The general idea is that a background process at the ETMS hub will automatically:

  • Monitor a Ground Delay Program (GDP) or Airspace Flow Program (AFP) for open slots.
  • Identify those slots that are in danger of going unused
  • Move other flights earlier to take advantage of those open slots
  • Move the open slots later
  • Update the databases with the changes
  • Send notification (EDCT updates) to the flight operators about the changes

The benefits of Adaptive Compression are:

  • Higher utilization of the airport/airspace capacity
  • Customers can be more proactive regarding constraints, restrictions, etc.
  • Reduced workload for the ATCSCC specialist/ATC Coordinator

What does this mean to operators?

When a flight is issued an Expect Departure Clearance Time (EDCT) as a result of a GDP or an AFP, the crew can expect that time to change as the program runs its course. This could mean that the EDCT will move earlier or later.

Since these changes are not sent to each individual operator (as they would be sent to dispatch in an airline situation), operators are encouraged to remain aware of what is happening in the NAS and to check their EDCT times regularly by either using the FAA's EDCT Lookup Tool, located at, or by staying in touch with ground control or clearance delivery.