When is the term "flight level" typically used?

The term "flight level" is typically used to denote an aircraft's altitude when flying at a standardized pressure setting of 29.92 inches of mercury (Hg) or 1013.25 hPa. This standardized measurement simplifies communication between pilots and air traffic controllers, particularly in congested airspace.

When an aircraft is operating at altitudes above 17,999 feet, it transitions into what is generally referred to as "flight levels." This is when altimeters are set to the standard pressure, allowing for consistent altitude reporting among various aircraft. The use of flight levels helps to ensure safe vertical separation between aircraft flying at high altitudes where weather conditions and other factors can change rapidly.

In contrast, the other options refer to altitudes either below or at this transition point, where local altimeter settings may still be in use, or cover specific landing procedures, which do not utilize the standardized flight level terminology.