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Airline On-Time Performance and Causes of Flight Delays

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Which airlines report on on-time performance and, since June 2003, on the causes of flight delays?
Carriers that have 0.5 percent of total domestic scheduled-service passenger revenue report on-time data and the causes of delay. In 2019, there are 17 carriers reporting these numbers. The reports cover nonstop scheduled-service flights between points within the United States (including territories) as described in 14 CFR Part 234 of DOT's regulations.

The reporting airlines are:

  • Alaska Airlines (AS)
  • Allegiant Air (G4)
  • American Airlines (AA)
  • Delta Air Lines (DL)
  • Endeavor Air (9E)
  • Envoy Air (MQ)
  • ExpressJet Airlines (EV)
  • Frontier Airlines (F9)
  • Hawaiian Airlines (HA)
  • JetBlue Airways (B6)
  • Mesa Airlines (YV)
  • PSA Airlines (OH)
  • Republic Airlines (YX)
  • SkyWest Airlines (OO)
  • Southwest Airlines (WN)
  • Spirit Airlines (NK)
  • United Airlines (UA)

BTS also compiles numbers for marketing carrier networks. These networks include carriers that operate flights under their own brands plus any regional code share partners that contract to operate flight under the markerting carrier's brand.

The marketing carrier networks are:

  • Alaska Airlines (AS)*
  • Allegiant Air (G4)
  • American Airlines (AA)*
  • Delta Air Lines (DL)*
  • Frontier Airlines (F9)
  • Hawaiian Airlines (HA)*
  • JetBlue Airways (B6)
  • Southwest Airlines (WN)
  • Spirit Airlines (NK)
  • United Airlines (UA)*

*Includes branded code-share partners

What types of flight delays are reported to BTS by the airlines?
Airlines that report monthly numbers of flight delays to the BTS began reporting information on causes of delays in June 2003. The airlines report the causes of delays in five broad categories:

  • Air Carrier: The cause of the cancellation or delay was due to circumstances within the airline's control (e.g. maintenance or crew problems, aircraft cleaning, baggage loading, fueling, etc.).
  • Extreme Weather: Significant meteorological conditions (actual or forecasted) that, in the judgment of the carrier, delays or prevents the operation of a flight such as tornado, blizzard or hurricane.
  • National Aviation System (NAS): Delays and cancellations attributable to the national aviation system that refer to a broad set of conditions, such as non-extreme weather conditions, airport operations, heavy traffic volume, and air traffic control.
  • Late-arriving aircraft: A previous flight with same aircraft arrived late, causing the present flight to depart late.
  • Security: Delays or cancellations caused by evacuation of a terminal or concourse, re-boarding of aircraft because of security breach, inoperative screening equipment and/or long lines in excess of 29 minutes at screening areas.

How were the reporting categories determined?
The U.S. Department of Transportation issued a final rule on reporting the causes of flight delays on November 25, 2002. The final rule followed two years of consideration.

DOT formed an Air Carrier On-Time Reporting Advisory Committee in August 2000 to consider changes to the current on-time reporting system so that the public would have clear information about the nature and sources of airline delays and cancellations. This task force recommended the creation of a reporting framework for collecting information about the causes of airline delays and cancellations.

In 2001, BTS conducted a pilot program with four airlines to test the monthly reporting of causation. BTS based the final rule on the recommendations of the task force, the results of its pilot project, its outreach efforts to the aviation community and comments received after a proposed rule was published in December 2001.

To view a copy of the rule, go to for Rule OST 2000-8164.

What flights does the reporting cover?
The rule requires carriers to report on domestic operations to and from U.S. airports.

How are flight delays calculated?

A flight is counted as "on time" if it operated less than 15 minutes later than the scheduled time shown in the carriers' Computerized Reservations Systems (CRS). Arrival performance is based on arrival at the gate. Departure performance is based on departure from the gate.

For how long have airlines reported on-time performance?
Airlines have reported on-time performance to the U.S. Department of Transportation since 1987. Reporting was modified in 1995 to include reporting of mechanical delays, which had not been included in the original rule. Monthly reports are released in the Air Travel Consumer Report.

What types of data are published?
The U.S. Department of Transportation publishes a monthly summary of airline on-time performance, including causes of delay, in the Air Travel Consumer Report.

The Bureau of Transportation Statistics publishes a variety of on-time and flight delay information.

Updated: Friday, March 29, 2019