In aviation terminology, the outside air temperature (OAT) or static air temperature (SAT) refers to the temperature of the air around an aircraft, but unaffected by the passage of the aircraft through it.
Most performance and flight planning graphs and tables use either degrees Celsius or Fahrenheit or both.
The Kelvin scale, however, is used for Mach number calculations.
For example, the speed of sound in dry air is where: Outside air temperature can be obtained from the aviation meteorological services, on the ATIS or measured by a probe on the aircraft.
When measured by the airplane's probe in flight, it may have to be corrected for adiabatic (ram effect) rise and friction,[3] particularly in high performance aircraft.