Traffic Flow Management (TFM)

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Airspace Flow Program (AFP)

An Airspace Flow Program (AFP) is a traffic management initative that identifies constraints in the en route domain of the NAS and develops a real-time list of flights that are filed into the constrained area, distributing Expect Departure Clearance Times (EDCT) to meter the demand through the area.

AFPs were introduced in the Summer of 2006 and marked a significant new step in en route traffic management. The principal goal for the initial deployment was to provide enhanced en route traffic management during severe weather events. However, the use of AFPs has been expanded to other applications.

How Do AFPs Work?

As traffic managers monitor traffic volume in the enroute portion of the National Airspace System (NAS), they are constantly looking for areas where the amount of traffic exceeds what that piece of airspace can handle at that time.

To assist them in doing this, they utilize a tool called a Flow Evaluation Area (FEA), which is a function of the FAA’s Enhanced Traffic Management System (ETMS). Basically, an FEA is a line in space that is drawn across a specific area. Traffic managers can then monitor the amount of traffic crossing that line. The FAA’s Flight Status Monitor (FSM) application is used to help analyze the traffic volume and, if needed, model a program to help manage it. An “acceptance rate” is set for each FEA - the amount of traffic that ATC determines can be accepted through that airspace in any given hour, half hour, or quarter hour.

Once the amount of traffic reaches a point where it is considered to be a potential issue, the FEA becomes a Flow Constrained Area (FCA). At this point, traffic managers begin looking at possible ways of metering the traffic across the FCA, to ensure that it does not exceed what ATC can actually handle. This may mean that ATC issues miles-in-trail restrictions, or reroutes designed to move traffic out of the constrained area.

If volume reaches a point where these initiatives are not sufficient, the specialist may decide to issue an AFP. Once this happens, specialists in the Command Center utilize the FSM application to model the AFP, much like they would a ground delay program. The AFP is designed to bring the amount of volume in each hour below the acceptance rate by delaying traffic, which is accomplished by issuing EDCTs.

Once an AFP is issued, the Command Center will send an Advisory that is accessible in the Advisories Database. The AFP will also appear on the Operational Information System (OIS) page. EDCTs will be accessible on the FAA’s EDCT Lookup Page.

Much like ground delay programs, (GDPs), AFPs can be run in Delay Assignment (DAS) mode, GAAP mode, or Unified Delay Program (UDP) mode. An increasing number of AFPs are being run in UDP mode, presenting a new set of implications to business aircraft. Learn more about Unified Delay Program mode.

It is important to understand the hierarchy of traffic management initiatives (TMIs). A ground stop is at the top of the hierarchy, since it is the most restrictive type of initiative and overrides any EDCT for a GDP or an AFP. A GDP is the second most restrictive program, so any EDCT for a GDP would, again, override an AFP. Note that, if a ground stop is lifted and the AFP is still in place, the flight will get a new EDCT for the AFP.

It is also important to note that the predicted demand through an AFP, and the weather impacting the area, may change substantially over time. When the conditions warrant, traffic managers will take steps to coordinate and implement revisions to the AFP, in an effort to reduce delays. In a revision, AFP entry slots are recomputed so that demand is again metered to meet capacity and new EDCTs are distributed. AFPs are also subject to adaptive compression, which can cause an EDCT to change numerous times during a program.

Where AFPs Are Used

When AFPs were created, traffic managers quickly recognized several “trouble spots” where they would initially, and most often, be used. This resulted in the creation of a set of pre-coordinated (known as “canned”) AFPs. These AFPs were designed to be implemented easily and with reduced coordination.

View the Seven “Canned” AFPs

Currently, most AFPs are focused on severe weather events in the eastern half of the United States. Specifically, they are typically used when lines of storms, or airmass (“popcorn”) storms, impact the NY metro and Boston metro areas, the Ohio Valley, Washington Center (ZDC), or the DC metro region. One primary decision tool utilized to determine whether AFPs are needed is the Collaborative Convective Forecast Product (CCFP).

AFPs are also used to manage situations such as increased seasonal demand into Florida, Mexico and the Caribbean, as well as equipment failures which result in loss of radar coverage and/or frequencies.

However, as AFP technology and procedures improve, it is expected that they will be utilized to manage airspace constraints throughout the NAS. This will result in the use of “ad-hoc” AFPs, which can be created and utilized anywhere in the NAS. If an ad-hoc AFP is created, it will be indicated on the OIS page, accompanied by a graphic representation and by an Advisory.

Options to Avoid AFPs

To avoid the delays associated with an AFP, the options are fairly straightforward - adjust the flight times to before or after the AFPs is in effect, or route around the AFP (if possible).

However, it is worth reiterating that it is critical for operators to file their flight plans well in advance, especially when the use of AFPs is possible. If a new flight plan is filed into an existing AFP, the flight will be treated as a late-filer (referred to as a “popup” by FAA). The flight will be assigned an EDCT consistent with the delay received by other flights filed to enter the AFP at about the same time. If the AFP is being run in UDP mode, the delays can be significantly worse. Learn more about UDP mode.

If a flight, that is already filed, is captured in an AFP, and another acceptable route is available that would take the flight out of the AFP, the flight plan may be refiled with the new route. However, it is important to note that some route-out options require the route to be filed exactly as it appears in the reroute Advisory or on the Current Reroutes web page.

Two of the most common AFPs, with specific route-out options are:

  • FCAA05 which captures flights through Indianapolis Center (ZID) and Cleveland Center (ZOB) from the west, destined to airports in northern Washington Center (ZDC), New York Center (ZNY) and Boston Center (ZBW).
  • FCAA08 which captures flights through Washington Center (ZDC) from the south, destined to airports in northern ZDC, New York Center (ZNY) and Boston Center (ZBW).