What does "Flight Level" refer to in aviation?

"Flight Level" in aviation refers to an aircraft's altitude, specifically defined in hundreds of feet above a standard datum plane, which is typically the mean sea level. When an aircraft is operating at a flight level, it is expressed in a format such as FL240, meaning the aircraft is flying at 24,000 feet. This standardized altitude allows pilots and air traffic controllers to ensure safe separation between aircraft, particularly when flying at cruising altitudes.

Other options refer to different aviation concepts: speed in knots pertains to the aircraft's velocity rather than altitude; the distance in nautical miles to a destination deals with navigation and distance management; and the angle of descent during landing relates to approach and landing techniques rather than the designation of altitude itself. Thus, the reference to "hundreds of feet" is central to the definition of flight levels in aviation.