APEppink

True, but how's that relevant?

Ideas c variance are tenuous but some people think it does and are working on it.

The plane accellerates relative to the ground, thus Newton's Law obviously comes into play.

"I think someone stated that an aircraft cruising at 45 knots into a 45 knot headwind would have zero kinetic energy, that is not correct. Kinetic energy relates to mass multiplied by speed squared and the speed for an aircraft in normal flight is the true airspeed, so any airspeed above Vs1 can still be swapped for gravitational potential energy even if the aircraft was moving backwards relative to the ground." No. It is correct. Even tho Kinetic Energy is a scalar (V^2 = V*V is a dot product). Kinetic energy exists only where there's a relative speed between the objects in question. Thus the guy sailing at 45kts IAS into a 45 kt headwind has no kinetic energy relative to the earth.

More Momentum.

E Everybody's ignoring F = m*a. An applied force is necessary to effect a linear accelleration. The force has to come from the air mass in the form of an initially reduced IAS. How else can it be?

"The aircraft is borne by the wind, and reference to GROUND SPEED has no impact at all on aerodynamics." Impossible. By F = m*a, an applied force is required to effect a linear accelleration. HOW does the airmass impart this force? SPECIFICALLY?