Definition
The actual speed of the aircraft through the surrounding air mass, corrected for the effects of air density (altitude and temperature). It differs from indicated airspeed because the airspeed indicator is calibrated for standard sea-level conditions, and as altitude or temperature increases, the air becomes less dense and the indicator reads lower than the aircraft's real speed through the air.
Plain English
How fast the airplane is really moving through the air around it, after accounting for the fact that thinner air at higher altitudes makes the airspeed gauge read low.
Context Anchor
Seen in flight planning, aircraft performance charts, cruise calculations, and navigation discussions where wind and fuel planning matter.
Derivation
True' here means 'actual' or 'real' — the speed corrected to reflect reality, as opposed to the raw 'indicated' reading on the gauge. 'Airspeed' simply means speed through the air (not speed over the ground).
Why Pilots Care
Accurate true airspeed is required for reliable navigation, fuel planning, and converting to groundspeed once wind is accounted for.
Intuition Check
Do not read “true” as meaning perfect or safer. Here it means the corrected, actual speed through the surrounding air, not ground speed and not simply the instrument reading.
Example Sentence 1
At 8,000 feet the airspeed indicator showed 110 knots, but the true airspeed was closer to 125 knots once corrected for altitude.
Example Sentence 2
Once true airspeed is known, subtracting the headwind component gives a reliable estimate of groundspeed.