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Flight level
Flight Level (FL), FL
At a glance
Meaning of Flight level
A constant-pressure surface expressed in hundreds of feet with the standard altimeter setting.
More about Flight level
Flight levels use 1013.25 hPa rather than a local pressure setting. For example, a level designation refers to the corresponding standard-pressure indication.
A flight level is not a guaranteed geometric height above mean sea level or terrain. Crews change pressure references according to the applicable transition arrangements.