|Year at end of period||Number of scheduled operations||Number of delayed flights||Average minutes of delay||Percentage of delay minutes due to:|
|Carrier||Extreme weather||National aviation system||Security||Late aircraft|
NOTES: On-time performance data is currently collected for 19 large carriers.
A flight is considered delayed when it arrived 15 or more minutes later than the schedule arrival (see definitions in Frequently Asked Questions). Average minutes of delay are calculated for delayed flights only. When multiple causes are assigned to one delayed flight, each cause is prorated based on delayed minutes it is responsible for. The diplayed numbers are rounded and may not add to the total.
SOURCE: U.S. Department of Transportation (USDOT), Research and Innovative Technology Administration, Bureau of Transportation Statistics, Airline Service Quality Performance 234. For more information, see http://www.transtats.bts.gov/OT_Delay/OT_DelayCause1.asp.