Airline cost glossary

A glossary of common terms used in the analysis of data on the United States airline industry. The US uses English units and flight lengths are therefore measured in statute miles and fuel usage in gallons. In contrast, the airline industry in the rest of the world uses similar quantities, but defined using metric system units, such as kilometers.

US airline carriers, whether privately owned or publicly traded are required under US law to file certain information with the US Department of Transportation, including financial and operating data. Therefore, relatively detailed information on even privately held US carriers is often available for public review through the website of the Bureau of Transportation Statistics.

Measure of aircraft productivity, calculated by dividing aircraft block hours by the number of aircraft days assigned to service on air carrier routes. Typically presented in block hours per day.

A common industry measurement of airline output that refers to one aircraft seat, available for sale, flown one mile, whether occupied or not. An aircraft with 300 passenger seats available for sale, flown a distance of 1,000 miles, generates 300,000 ASMs.

Also known as Aircraft Hour. The number of block hours for a given (revenue) flight is the time from the moment the aircraft pushes back from the departure gate revenue flight until the moment the aircraft arrives at the arrival gate following its landing (equal to the flight time for the flight plus the taxi time). The number of block hours for an airline for a given period of time (like a year, quarter or month) is a measure of the total time that its aircraft were in use during that period. Block hours are the industry standard measure of aircraft utilization (see above).

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