(Billions of ton-miles)
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).