QFE is a Q code used by pilots and air traffic control to refer to the barometric altimeter setting which will cause an altimeter to read height above a particular runway threshold. An altimeter set to QFE will therefore read zero when on the ground at the beginning of the runway. This setting may be used during take off and landing and when flying in the circuit. A mnemonic for the code is "Q Field Elevation".

ATC will update pilots with the QFE when necessary. A typical radio conversation might go:

• Pilot: Golf Whiskey Alpha Charlie Foxtrot, requesting taxi clearance for local VFR
• ATC: Golf Charlie Fox, taxi to Alpha for 25 right hand, QFE niner-niner-eight millibars
• Pilot: To Alpha, 25 right, QFE niner-niner-eight, Golf Charlie Fox

Here, the pilot of G-WACF (who is on the ground) requests a taxi clearance and is told to taxi to holding point A for runway 25, the circuit is right handed and QFE is 998 millibars. The pilot acknowledges the information by repeating it back to ATC.

In most parts of the world, QFE is given in millibars (or hectopascals, which is the SI unit). Whilst the Royal Air Force and some European private pilots still use QFE, it is largely obsolete in commercial aviation, where QNH is preferred for take off and landing. In the USA and Canada QFE is rarely used.