What does the term "flight level" signify in aviation?

The term "flight level" signifies a standardized altitude that is expressed in hundreds of feet above sea level. This system is especially relevant in IFR (Instrument Flight Rules) operations, where aircraft are separated vertically at specific altitudes. Flight levels are particularly useful as they help ensure safe vertical separation between aircraft flying at high altitudes.

In this context, flight levels are typically referred to using "FL" followed by a number (for example, FL350 indicates a flight level at 35,000 feet). This system minimizes confusion with altimeter settings and the variations caused by atmospheric pressure changes, as all aircraft operating at a given flight level are maintaining the same reference pressure, usually 29.92 inHg.

Understanding this framework is crucial for pilots and air traffic controllers to maintain safe distances between aircraft and to coordinate traffic effectively in the busy airspace, especially during instrument flight conditions.