Causes of Delays

According to the FAA, reportable delays are delays to IFR traffic of 15 minutes or more, experienced by individual flights. Delays may result from detaining an aircraft at the gate, short of the runway, on the runway, on a taxiway, and/or in a holding configuration anywhere en route.

Some delays are not reported. Linear holds (e.g. speed reductions) and/or pilot initiated deviations around weather cannot be accounted for and are not included in the reporting process. Delays that are due to mechanical or other aircraft operator/company problems are not reported. Taxi time spent under the control of non-FAA entities, such as company or airport ramp towers, are not included in delay calculations.

Other delays can be region specific, such as in the NY Metro area. There are many days when low ceilings and/or winds can conspire to keep the arrival rate low and cause excess airborne inventory. Also, on days when the ceilings and visibility are low there may be issues with competing ILS approaches. During these times, ATC may hold airborne traffic for one airport while they land a stream at another. Finally, due to the amount of overhead traffic, departure delays may begin to develop because there is no way to get departing traffic up into the overlying airspace, referred to as the “overhead stream”.

Delay calculations begin when the aircraft enters ATC jurisdiction – for example, calls for taxi on ATC controlled airport property, or enters a holding pattern. When delays are issued with a Ground Delay Program, the EDCT minus the proposed departure time and the average taxi time, equals the delay time. These delays are attributed to the arrival airport. Delay calculations end when the aircraft departs or exits holding.

All airports have calculated average taxi times for all runway configurations. These values are not included in reported delays.

Delay calculations are entered each day by all air traffic facilities except flight service stations, Service Area Offices and FAA Headquarters. The data is entered into software called the Operations Network (OPSNET). This information is forwarded to the ATCSCC for analysis.

Delays are normally attributed to the following five factors:

• weather
• volume
• equipment
• runway
• other

The “other” category is used for items such as security issues, aircraft accidents, noise abatement, flight checks, etc.

A common question is, “Why do aircraft that push back or call for clearance after me, depart ahead of me?” The answer is that, although air traffic control operates on the “first come, first served” principle, controllers are expected to use their best judgment in determining the safest and most efficient flow of traffic considering the different types of aircraft and whether priority handling has been requested.

An example of one of these considerations might be aircraft that are departing over different departure fixes. Depending on conditions, some of those fixes may be affected by TMIs while others are not.

The best ways to mitigate delays are to stay informed, using the information available on the FAA’s website: www.fly.faa.gov/ois and to plan flights to operate during the non-peak times for the airport or areas of congested airspace.