An altitude of constant atmospheric pressure related to a reference datum of 29.92 inches of mercury, stated in three digits in hundreds of feet. In the US, the FL system is used for flights at and above 18,000 ft msl.
Altitude expressed in hundreds of feet. FL 350 is equal to 35,000 feet. Below about 20,000 feet, Flight Levels are not used. Military and some older civilian pilots may give their altitude in Angels. An Angel is equal to 1,000 feet. A pilot may also report his altitude as "level at 18,000". This is not the same as a Flight Level, but means that he has stopped climbing or descending at the indicated altitude.
The altitude expressed in hundreds of feet indicated on an altimeter set to 29.92 in. of mercury or 1013.2 mb. abbreviation: FL Fr: niveau de vol
(FL) An isobaric area of constant air pressure used for aircraft separation at high altitudes. The flight level shows the altitude above standard air pressure, measured in hundreds of feet. Thus, flight level 200 is approximately 20,000 ft (6,000 m) above sea level.
A level of constant atmospheric pressure related to a reference datum of 29.92 inches of mercury. i.e. Flight Level 250 represents a barometric altimeter indication of 25,000 feet.
Altitude in hundreds of feet, e.g. "FL200" = 20,000 feet. Usually used in Air Traffic Control. A standard altimeter setting of 29.92" is used.
Flight level is the nominal altitude of an aircraft referenced to a standard pressure datum, as opposed to the real altitude above mean sea level.
Altitude: "Snake one, flight level 2-1-0" (player 'snake one' is flying at an altitude of 21,000 ft.)
A surface of constant atmospheric pressure that is related to a specific pressure datum (1013.25 hPa) and is separated from other such surfaces by specific pressure intervals. It is conventionally given a numerical value to the nearest 1000 ft in units of 100 ft in accordance with the structure of the ICAO Standard Atmosphere. For example, the 500-hPa level is written as FL 180, the ICAO standard height being 18 289 ft.
In aviation, a Flight Level is a standard nominal altitude of an aircraft, referenced to a world-wide fixed pressure datum of 1013.25 mbar or the equivalent setting, 29.921 in Hg (the average sea-level pressure). It is not necessarily the same as the aircraft's true altitude above mean sea level. Altitudes are only called by their three-digit flight level above Flight Level 180 (18,000ft).
