|Year||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 20 large carriers.
A flight is considered delayed when it arrived 15 or more minutes later than scheduled. Average minutes are calculated for delayed flights only. When multiple causes are assigned to one delayed flight, each cause is prorated based on delayed minutes for which it is responsible. The numbers above are rounded and may not add up to the total. Additional information is available at http://www.bts.gov/help/aviation/index.html.
SOURCE: U.S. Department of Transportation, Research and Innovative Technology Administration, Bureau of Transportation Statistics, Airline Service Quality Performance 234, available at http://www.transtats.bts.gov/OT_Delay/OT_DelayCause1.asp as of August 2008.