Definition
The altitude at which a flight is planned or actually conducted, measured above mean sea level (MSL) and used as a reference when requesting weather briefings, filing flight plans, and reviewing forecasts along a route.
Plain English
The height above sea level you plan to fly at — the number you give the briefer or put on your flight plan so they can tell you what weather to expect at that level.
Context Anchor
Seen when requesting or reviewing a weather briefing, because weather information such as winds, temperature, clouds, icing, and turbulence can change with height.
Derivation
Flight comes from an old word meaning the act of flying. Altitude comes from Latin altus, meaning high. Together, flight altitude simply points to the height used while the aircraft is flying.
Why Pilots Care
Weather varies sharply with altitude. Winds, temperatures, icing, turbulence, and cloud layers can be very different a few thousand feet up or down, so giving the briefer your intended flight altitude is what makes the briefing relevant to your actual flight.
Intuition Check
Do not read flight altitude as the exact height the airplane will hold for the entire trip. In this context, it means the planned operating height or heights used to get the right weather information.
Example Sentence 1
When requesting the standard briefing, she gave the briefer her departure time, route, and proposed flight altitude of 7,500 feet.
Example Sentence 2
Selecting a higher flight altitude allowed the aircraft to fly above the reported cloud layer.