NOTE: A revenue ton-mile is equal to 1 ton that is carried 1 mile and measures
utilization of air freight services. For those planes that carry both freight
and passengers, available freight ton-miles are calculated by subtracting available
seat-miles times 0.1 from total available ton-miles. The data include both transborder
and foreign flights by U.S. carriers, but do not include any flights by foreign
carriers. The drop in 2001 reflects the impact of the terrorist attacks of Sept.
11, 2001, on aviation, including several days in which commercial air operations
were suspended.
SOURCE: U.S. Department of Transportation, Bureau of Transportation Statistics,
Office of Airline Information, Air Carrier Traffic Statistics (Washington,
DC: May 2002).
