A flight level (FL) is a nominal altitude flown by aircraft above the transition altitude, calculated using a standard altimeter setting of 29.92 inches of mercury or 1013.2 hectopascals. It ensures all aircraft in the upper airspace use the same pressure reference, preventing midair collisions caused by local weather variations. For example, FL350 represents an altitude of 35,000 feet under standard conditions.
Heard on the job
Center, Delta one niner heavy is climbing to FL350.
Related terms
Transition
A published flight path connecting the en-route structure to an approach or departure procedure.
Air corridor
A designated block of airspace through which aircraft are required to fly.
Holding pattern
A holding pattern is a standardized racetrack-shaped flight path used to delay an aircraft in flight.