What Is Indicated Airspeed? Definition & Meaning in Aviation
Indicated airspeed (IAS) is the speed shown on the aircraft’s airspeed indicator, based on the pressure of the air rushing into the instrument.
In plain language
IAS tells pilots how well the wings are flying, which is why limits such as stall speed are given in IAS. It is lower than TAS at altitude.
Example
During approach, pilots fly published indicated speeds rather than ground speeds.
Why it matters
IAS is what pilots fly, because aircraft limits are expressed in it. It is why the speed pilots quote can be far lower than the speed you see on a tracker at cruise.