Indicated airspeed (IAS)

Flight planning

IAS is the speed shown on the aircraft’s airspeed indicator, before correction for instrument and position errors. It is not the aircraft’s speed over the ground.

German term: Angezeigte Fluggeschwindigkeit (IAS)
Abbr.: IAS

The instrument uses the pressure difference between the pitot and static systems. Correcting IAS for instrument and position errors gives calibrated airspeed (CAS); further corrections lead to equivalent and true airspeed. Flight-manual limitations and target speeds use a stated speed basis, often KIAS (knots indicated airspeed). Wind changes groundspeed, not IAS directly.

In practice

Use the speed basis specified in your aircraft’s flight manual for approach speeds and limitations. A GPS groundspeed is not a substitute for IAS, especially in a headwind or tailwind.

Related terms

Official sources

FAA – Pilot’s Handbook of Aeronautical Knowledge

Content reviewed: 2026-11

For general information only. Always use official sources, your aircraft's flight manual and current national rules for flight decisions.