DY, I see now that it is obvious that the person being Zarul doesn’t help, since the Gemara applies this to the moving wagon. He is moving in the wagon, just as he’s moving in the airplane. Obviously, we have to be Mechalek between Tuma going over him and him going over the Tuma. The first is through Ohel and the second is Magga.
I have one more Hetter up my sleeve. The airplane itself is a Tzamid Passil, since it is bigger than 40 Saah, so it isn’t Tammei, and it is sealed. The only question I have is that although a Tzamid Passil is allowed to have an opening, that is only a break, but not its actual opening. Since the airplane has openings that it depends on and it gets its compressed air from the engines, perhaps it is not a valid Tzamid Passil.