Seasonally adjusted, yearly averages
Index: 1990 = 100.0
NOTE: The average travel time is the Travel Time Index multiplied by the base year (1990) travel time in minutes and divided by 100. Because the Travel Time Index controls for distance and other factors, the average travel time may differ from the actual travel times of specific flights. The Travel Time Variability Index is based on the standard deviation of actual travel time.
SOURCE: U.S. Department of Transportation, Bureau of Transportation Statistics, calculations based on Airline Service Quality Performance data, March 2004.