It was the statement that, "once in the air, an aircraft is not affected my wind (except relative to ground)" which was confusing. It made me picture the aircraft suddenly having the headwind flow of 50knots over the wings removed as it is now "in" the body of air rather than having the body of air flow over it.
Being "in" the body of air doesn't mean that the aircraft loses any speed relative to the air. Yours was apparently a kind of the "plane on a conveyor belt" confusion. The plane does not push itself into the air by spinning its wheels quickly enough
(in which case it would indeed lose its airspeed as soon as it gets airborne).