Air Speed is the speed indicated by the in flight instruments and it is not used to calculate how long will the flight takes. True speed considers the diference betweet airspeed and temperature e etc… Ground speed considers the winds and is better used to calculate how much time you are going to spend during a flight.
ATC uses always air speed… The trip is calculated by ground speed. Ok. But some reference documents use true speed, e.g: airplanes specs.
I think it is correct. Please correct if not.
Besides that, how can I find true speed in IF? I can just find air speed and ground speed.