FLIGHT LEVEL [ICAO]

Definition

• A surface of constant atmospheric pressure which is related to a specific pressure datum, 1013.2 hPa (1013.2 mb), and is separated from other such surfaces by specific pressure intervals.
  Note 1: A pressure type altimeter calibrated in accordance with the standard atmosphere:
  a. When set to a QNH altimeter setting, will indicate altitude;
  b. When set to a QFE altimeter setting, will indicate height above the QFE reference datum; and
  c. When set to a pressure of 1013.2 hPa
  (1013.2 mb), may be used to indicate flight levels.
  Note 2: The terms ‘height’ and ‘altitude,’ used in Note 1 above, indicate altimetric rather than geometric heights
  and altitudes.

References

• Pilot Controller Glossary, Federal Aviation Administration, 2023