true air speed

true air speed (TAS)

Relationship between IAS and TAS at various heights.The actual speed of an aircraft relative to the air through which it flies (i.e., the calibrated air speed corrected for temperature, density, and compressibility). If the compressibility effects are ignored, then the IAS equals the product of the TAS and the square root of the relative density. Similarly, the TAS is related to the Mach number by the square root of the relative temperature.