Airline Data Project Provides statistical and financial data for the airline industry
Bureau of Transportation Statistics (BTS) Part of the division of the Research and Innovative Technology Administration of the U.S. Department of Transportation. The BTS compiles, analyzes, and publishes statistical information on U.S. transportation systems. Data downloadable as CSV file (1995-present).
International Transport Forum Contains data relevant to a range of transport policy issues including investment & maintenance, transport statistics, emissions, road taxation and safety.