What Is True Airspeed? Definition & Meaning in Aviation
True airspeed (TAS) is an aircraft’s actual speed through the air, corrected for altitude and temperature.
In plain language
At high altitude the air is thin, so the instruments show a lower speed than the aircraft is really moving through the air. TAS is the corrected value.
Example
An airliner cruising at 35,000 feet may have a TAS far higher than the airspeed shown on the pilot’s instruments.
Why it matters
TAS is the speed used to compute performance and fuel burn. Comparing TAS with ground speed reveals the wind an aircraft is flying in.