What is a TMI (Traffic Management Initiative)?

Traffic management initiatives (TMIs) are techniques used by air traffic control to balance demand with capacity when conditions are not ideal, either at an airport, or in a section of airspace.

The intent behind traffic flow management (TFM) is to balance demand with capacity – both at airports and in airspace. In other words, air traffic managers try to ensure:

-               There are not too many airplanes in one place at one time.

-               The system is running efficiently.

Traffic management initiatives (TMIs) are techniques used by air traffic control to balance demand with capacity when conditions are not ideal, either at an airport, or in a section of airspace.

Ironically, operators who actually know about TMIs often associate them with delays. But, in reality, TMIs exist to minimize overall delays.

Airport-Specific (Terminal) TMIs

Some TMIs are designed to deal with the issue of too many airplanes arriving at an airport during a certain period of time. Each airport has a certain rate at which they can handle arriving traffic, known as the airport acceptance rate (AAR), which can change depending on weather, construction or other factors. If the number of airplanes heading to that airport are above that AAR, traffic managers must slow things down to keep it manageable.

Ground Delay Programs (GDPs)

A GDP is a TMI where aircraft are delayed at their departure airport in order to reconcile demand with capacity at their arrival airport. Flights are assigned an expected departure clearance times (EDCTs), which ensure that they arrive at the affected airport when they can be accommodated.

GDPs will normally be used when an airport’s arrival capacity has been reduced by weather or other factors for a sustained period of time. Note that GDPs affect arrivals to a constrained airport, not departures from that airport. Also, they are airport-specific – each GDP only affects a single airport.

Ground Stops

Ground stops are the most restrictive form of TMI because they hold all aircraft, within the scope of the ground stop, at their departure airports until conditions at the destination airport allow for their arrival.

This type of TMI is typically used for shorter-term problems at an airport, such as an unexpected spike in arrival demand during a particular hour or thunderstorms affecting an airport.

Note that ground stops only affect arrivals to a specific airport (not departures) and, like GDPs, are airport specific. Also, ground stops do not generate EDCTs. The stop simply continues until its “update time,” after which it is extended, expanded or cancelled.