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FLIGHT LEVEL

General Aviation

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A level of constant atmospheric pressure related to a reference datum of 29.92 inches of mercury. Each is stated in three digits that represent hundreds of feet. For example, flight level (FL) 250 represents a barometric altimeter indication of 25,000 feet; FL 255, an indication of 25,500 feet.

Source FAA Pilot/Controller Glossary · checked 2026-08-25

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