Ok...Just a thought model When an aircraft is in flight, the earth pulls on the airplane (weight). The wings generate lift to support the weight. However, the aircraft is also pulling up on the earth with the same force. So, techincally the earth has momentum imparted to it in the upward direction when the aircraft flies overhead. I know that the "change" in the earth's velocity will be ridiculously small (there would be no way to measure or feel it) due to the earth's massive size. But don't we impart momentum to the earth evreyday? When I drive my car, I push backwards on the earth, even when we all walk, we push backwards on the earth. I realize that it probably all cancels, at some point in time, as for every person walking eastbound, there is probably someone walking westbound or stopping. But what about the airplane? Do we indeed impart momentum to the earth, in the upward direction when an aircraft flies overhead, and there is no downwash reaching the earth because it has been dissipated?