Ok I understand that they are impure if they enter a cemetery according to the laws of Moses. But let's put this nonsense into perspective.
1 Even if he is of a priestly class,nobody flew in Moses time so I have doubts about flying over cemetery air space is covered.
2 there is no temple so he's not exactly in the same position as those who served in the temple of ancient times is he.? It's not like they are going before the Holy of Holies.
3 there are ways to purify yourself after becoming unclean from a dead body or sitting next to an unclean woman, so he can simply go do that when he lands.
4 these guys walk over dead bodies all the time without even knowing it. There are so many layers upon layers in that section of the world,and so many people buried where they dropped during wars, it's impossible to know whether or not if there's a three thousand year old body under foot or not. There is a big difference between recently deceased and long dead as far as disease is concerned. No transfer of contamination should be passed by flying in a plane over a cemetery. The whole thing is ridiculous and El Al should continue to discourage this behavior.