Tools Used for Traffic Flow Management

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Traffic Management Initiatives (TMIs) are programs and tools that ATC may use to manage air traffic. These initiatives can take a number of forms, depending on the need and situation. Some TMIs are used to manage excess demand or a lowered acceptance rate at a particular airport. Other TMIs are used to manage traffic issues in the en route environment. TMIs can generally be divided into 2 categories - terminal and en route.

Terminal TMIs are airport-specific, in that they directly impact arrivals into a particular airport. This is contrasted with programs like AFPs which can affect numerous airports due to en route issues.

It is important to note that terminal TMIs are airport-specific. For example, if there is a ground stop or GDP at White Plains, NY (HPN), flights to Morristown, NJ (MMU) are not affected by that TMI.

Enroute TMIs, as their name implies, are used to manage air traffic in the en route segment of flight. Only one en route TMI can actually generate an EDCT for a flight - the Airspace Flow Program (AFP). AFPs behave in a similar fashion to GDPs, but control flights into a particular block of airspace instead of a particular airport.

The remaining en route TMIs can generate flight delays either before departure, or while enroute. However, many of these initiatives are implemented to avoid delays altogether, as in the case of SWAP or preferred routes.

Commonly Used Traffic Management Initiatives

While there are quite a few TMIs that traffic managers can utilize on a daily basis, there are several that are commonly used and that operators should be the most familiar with.

Ground Stop (GS)

A Ground Stop is an initiative requiring aircraft that meet specific criteria to remain on the ground at their origination airports due to a constraint at their destination airport. They are generally used for relatively short-term constraints, lasting 2 hours or less. Ground stops are the most restrictive form of TMI. More information about Ground Stops.

Ground Delay Program (GDP)

A Ground Delay Program (GDP) is a traffic management initiative where aircraft are delayed at their departure airport in order to reconcile demand with capacity at their arrival airport. Flights are assigned departure times, which in turn regulate their arrival time at the impacted airport. GDPs can be run in one of three different modes: Delay Assignment (DAS) mode, GAAP mode, and Unified Delay Program (UDP) mode. The UDP mode GDPs are now the most commonly used form of GDP. More information about Ground Delay Programs

Airspace Flow Program (AFP)

Introduced in 2006, Airspace Flow Programs (AFPs) marked a significant new step in en route traffic management. An AFP is a traffic management process that identifies constraints in the en route system, develops a real-time list of flights that are filed into the constrained area, and distributes expect departure clearance times (EDCTs) to meter the demand through that area. Like GDPs, AFPs can be run in DAS, GAAP, or UDP mode. More information about Airspace Flow Program

Miles-in-Trail (MIT)/Minutes-in-Trail (MINIT)

Miles-in-trail describes the number of miles required between aircraft departing an airport, over a fix, at an altitude, through a sector, or along a route. MITs are used to apportion traffic into a manageable flow, as well as provide spacing for additional traffic (merging or departing) to enter the flow of traffic. More information about Miles-in-Trail

Traffic Management Advisor (TMA)

Traffic Management Advisor (TMA), otherwise known as time-based metering, is a relatively new air traffic management tool that seeks to schedule aircraft to an active runway threshold with the least amount of delay. The idea is to assign delays on the ground to prevent excessive holding, thereby saving fuel and increasing safety. More information about TMA

Reroutes & Severe Weather Avoidance Plan (SWAP)

When air traffic needs to be moved away from or into a particular area of airspace, traffic managers will implement reroutes (either optional or required) that move traffic to specific routes needed for optimized traffic flow. A specific application of reroutes is known as the Severe Weather Avoidance Plan (SWAP), which is a formalized program that is developed for areas susceptible to disruption in air traffic flows, usually caused by thunderstorms. More information about reroutes and SWAP

Additional Terminal TMIs

Special Traffic Management Program (STMP)

An STMP is a set of planned traffic management procedures implemented to effectively manage the increased air traffic demand expected for a given special event. STMP NOTAMs are issued in the Notices to Airmen Publication. Learn more.

High Density Traffic Airports (HDTA)

There are certain airports that require unscheduled operations to acquire a reservation prior to operating at the airport. These airports include John F. Kennedy International Airport (JFK), Ronald Reagan Washington National Airport (DCA), LaGuardia Airport (LGA) - for specified periods of the day only, and Chicago O'Hare Airport (ORD). Learn more.

Additional Enroute TMIs

Collaborative Trajectory Options Program (CTOP)

CTOP is a new type of TMI, currently in development, that automatically assigns delay and/or reroutes around one or more FCA-based airspace constraints in order to balance demand with available capacity. The unique feature of CTOP is that it allows for user preferences in route selection. CTOP is expected to be released in March 2014. More information about CTOP

Other En Route Tools

There are additional tools that traffic manager use to manage en route traffic. These tools include:

Latest News

FAA's New CTOP Initiative Aims to Reduce Airspace Congestion
December 13, 2012
In 2013, the Federal Aviation Administration (FAA) is slated to implement a new traffic management initiative known as the Collaborative Trajectory Options Program (CTOP), which will better balance demand with available capacity. Under a CTOP initiative, operators submit alternative routes of their choice around or away from a constraint, thus providing additional options for air traffic controllers to expedite flights away from congested airspace. Flights that have submitted a trajectory option set (TOS) could be exempt from ground delays or in-flight reroutes associated with such constraints. Read more about CTOP.

General TMI Guidance

All aircraft that meet the specified criteria of the TMI are included. Aircraft that are impacted by a TMI and require priority handling because of some special circumstance may be accommodated. In addition, operators are expected to comply with issued TMIs. However, in accordance with Federal Air Regulations Parts 91, 121 and 135, all operators have the right of refusal of a specific clearance and may elect an alternative. Alternatives include, but are not limited to, ground delay, diversion to other airports, or request to stay on the filed route.

Air traffic controllers and Traffic Management specialists strive to ensure TMI compliance. In special circumstances, they may request exemptions for certain aircraft. In the case of GDPs or AFPs, the Air Traffic Control System Command Center (ATCSCC) monitors compliance with the Flight Schedule Monitor (FSM). The FSM is a computer program used by the ATCSCC and customers to monitor aircraft within the NAS.

In the case of a GDP or an AFP, non-compliance with a TMI can result in an overabundance of airplanes or in unused slots that cannot be filled at the destination airport or volume of airspace. This can cause holding, diversions, extensions, and revisions of the GDP/AFP and/or Ground Stops, all of which lead to more delay. In short, everyone pays the price for non-compliance.

More information regarding what TMIs are currently in effect in the NAS can be found on the the FAA OIS website, which provides near real-time status information about the NAS. Pilots may also receive information through the local air traffic facility (including flight service stations). Learn more about OIS.