Plain English Meaning

These are how fast the airplane is really moving through the air, not just what the airspeed gauge shows. At higher altitudes the air is thinner, so the gauge reads lower than the airplane's real speed through the air.

Full Definition

True airspeeds are the actual speeds of an airplane through the surrounding air mass, corrected for the effects of altitude and non-standard temperature on the indicated airspeed. As altitude increases, air becomes less dense, so the airspeed indicator under-reads — meaning true airspeed is higher than indicated airspeed at altitude.

Context Anchor

Seen in aircraft performance discussions, especially when comparing how a turbocharged airplane performs at higher altitudes.