Flight level is a term used to describe the altitude of an aircraft in relation to the average sea level. Distinguishing between measurements using average sea level and true sea or ground level, pilots will refer to “flight level” specifically. For high flight, flight level is the most crucial measurement; while at lower altitudes, the true height of the aircraft relative to objects on Earth is important. The aircraft has the capacity to measure both.
Altitude meters for calculating the altitude of an aircraft depend on changes in the air pressure as the planes rise. To calculate flight level, they are calibrated with average sea level as the baseline. To get a true height reading, the altimeter needs to be recalibrated. Aircraft may have a different altimeter or switch to toggle between flight level and altimeter setting to get both measurements, depending on how the dashboard is designed.
The flight level is given in units of hundreds of meters. An aircraft at flight level 20 is 2000 meters above average sea level, for example. When the pilots give readings, they will go ahead of them with “flight level” so listeners know what the reference frame and baseline are used. This is important to avoid loose air collisions. Two planes rely on local altimeter settings can end up crashing even though their altimeters have different measurements, while when both are flight level measurements, they can avoid each other by sticking to specific tracks on board in the same area.
Airspace is checked at various heights to determine what kind of vehicle may be present, the rules they must follow, and how traffic will be routed and prioritized. Flight attendants use flight schedules and other reports from pilots along with radar and similar tools to keep track of what’s happening in their airspace so they can make recommendations to pilots. These may include orders to climb or drop height to avoid collisions, as well as instructions on how to approach airports and stripes. Flight controllers also maintain local altitude data for pilots who need to calibrate their altimeters.
In many countries, the airspace is divided into tracks, with flying at a certain altitude range depending on the direction they go in and the routes they take flight. This standardizes routine air traffic, making it safer to fly. It can also eliminate confusion in relief when an aircraft must be prioritized due to engine problems or other issues that require a quick landing.
- Flight level is measured by an aircraft altimeter.
- To calculate flight level, the aircraft altimeter measures changes in air pressure as the aircraft climbs.