- QFE (Field Elevation) Green
- Altimeter reads height above the airport.
- If set to 0 at the airport, altitude shows distance from the ground.
- QNH (Mean Sea Level — MSL) Blue
- Altimeter reads altitude above sea level.
- Used for general flight operations below transition altitude.
- Standard (Flight Level — FL) Red
- Altimeter set to 1013.25 hPa (Standard Pressure).
- Used above transition altitude for uniform separation.
Pilots adjust altimeter settings for accurate altitude readings ❗️