The number of flights not departing or arriving on time, cancellations, and diversions are measures of service quality. These indicators are strongly seasonal and are affected by weather and heavy demand in winter and summer months, respectively.
|Flight On-Time Performance||Dec-06||Dec-07|
|Number of scheduled flights||573,345||565,587|
|Percent change from same month previous year||1.84||-1.35|
|Percent of flights not arriving on time||29.32||35.40|
|Percent change from same month previous year||0.88||20.75|
|Percent of flights not departing on time||26.81||30.74|
|Percent change from same month previous year||3.59||14.66|
|Percent of cancelled flights*||2.96||3.20|
|Percent change from same month previous year||56.08||8.23|
|Percent of diverted flights**||0.23||0.24|
|Percent change from same month previous year||19.18||3.51|
* Also counted in flights not arriving or departing on time.
** Also counted in flights not arriving on time.
NOTES: The current value is compared to the value from the same period in the previous year to account for seasonality. Data are available for those carriers that had at least 1% of domestic enplanements in the previous year. The last 25 months of data include only carriers that reported in each of the last 25 months to retain comparability. Earlier data includes all reporting carriers.
A scheduled operation consists of any nonstop segment of a flight. The term "late" is defined as 15 minutes after the scheduled departure or arrival time. A cancelled flight is one that was not operated but was listed in a carrier's computer reservation system within seven calendar days of the scheduled departure. A diverted flight is one that left from the scheduled departure airport but flew to a destination point other than the scheduled destination point.
A trend line has been provided for flights not arriving on-time. The trend has been calculated through a statistical procedure called Structural Modeling, in which the time series under study is decomposed into seasonal, trend and irregular components. For further information on this statistical procedure, see: S.J. Kiipman, et al., Structural Time Series Analyzer, Modeler and Predictor (STAMP), London: Timberlake Consultants Ltd., 2000.
The dramatic changes in the September 2001 data reflect the impact of the terrorist attacks on September 11, 2001, on aviation, including several days in which commercial air operations were suspended.
Certain flights originating at O'Hare airport and operated by American Airlines (181flights in April 2002) and United Airlines (256 flights in April 2002) between April 24, 2002 and May 8, 2002 are not included in the calculations due to the participation of these carriers in a pilot test program for enhanced baggage screening. A list of affected flights is available from BTS.
SOURCE: U.S. Department of Transportation, Research and Innovative Technology Administration, Bureau of Transportation Statistics, Airline Service Quality Performance data, as of February 2008.