4 ms·Do you know why the plane doesn't use GPS as a backup method for airspeed measuring?by genwin 14y agoDo you know why the plane doesn't use GPS as a backup method for airspeed measuring?whiskers 14y agoBecause airspeed is relative to the speed of the air around you (not relative to your position on the earth). The pitot tubes (which caused the initial problem by icing over) are there to determine exactly that.genwin 14y agoDoh! Finally, it makes sense.