What is defined as "Flight Level" in aviation?

"Flight Level" in aviation refers specifically to a vertical aircraft altitude that is expressed in hundreds of feet above sea level, with reference to standard atmospheric pressure. This is a system that allows pilots and air traffic controllers to communicate ascent and descent in terms of flight levels, which are standardized to ensure safety and consistency in the airspace.

When aircraft are flying above a certain altitude, typically transitioning to controlled airspace, they instead refer to altitude in terms of flight levels (e.g., FL280 refers to 28,000 feet). This system mitigates discrepancies in local atmospheric pressure that might affect altitude readings. The other provided choices do not pertain to the specific concept of flight level; horizontal speed, distance to the runway, and an aircraft’s operating weight refer to different parameters of flight that are unrelated to the defined vertical altitude concept of flight levels.