Tracker readouts
Altitude vs Flight Level
Altitude and flight level are related but not identical ways of expressing vertical position. The distinction matters when reading aviation data or listening to air traffic communications.
By TransitSatellite · Reviewed October 20, 2026
Altitude can use a local pressure reference
Below the transition level used in a region, aircraft altimeters are commonly set using a local pressure reference so altitude can be related to mean sea level.
Public trackers may display pressure altitude, geometric altitude, or a processed value depending on the data source.
Flight levels use a standard pressure setting
At higher altitudes, aviation uses flight levels based on a standard pressure reference. A flight level is written without the final two zeros, so FL350 corresponds nominally to 35,000 feet on the standard pressure setting.
In the United States, FAA guidance uses flight levels beginning at 18,000 feet MSL under standard operating rules.
Tracker altitude needs context
A number on a public map should be read together with the provider’s field definition. Pressure-derived altitude and satellite-derived geometric altitude are not always numerically identical.
That difference does not necessarily indicate an error; the values can be based on different reference systems.
Common questions
What does FL350 mean?
It means Flight Level 350, nominally corresponding to 35,000 feet on the standard pressure reference.
Why can two trackers show slightly different altitude values?
They may use different source fields, reference systems, corrections, or update timing.
Sources
Flight tracker search
Start with a flight number or route and open the current tracking source.
Search flightsTransportation globe
See the airport layer on the existing TransitSatellite 3D globe.
Open globe