How do people do this, generally?
I have played WW2 games that featured an air attack, but it wasn't very satisfying visually. We wrote down what a strike consisted of ("12 x Avenger w. torpedo") on bits of paper, screwed them into balls (so the target didn't know what the strike comprised), and positioned them next to the target during the move they arrived. We resolved combat and then tossed the paper because you didn't have time for two strikes in the same game.
Being 6 times faster than the fastest ships, one move was as long as any grotty bit of paper spent on the table.
In a WW1 context it seems to me that some effort to depict actual planes makes sense. In 1918, they're only twice as fast as the fastest ships, so a squadron of, say, Cuckoo torpedo bombers would be like a small but very fast destroyer flotilla, and would be on table for quite a long time.
Zeppelins are simple – at 12,000 feet, an altitude of 4,000 yards, you would I guess place a model on a stand atop a wire 16" tall. It is then at the correct scale height.
For small planes is there a better option than bits of paper? Could one print plan views of planes on clear acetate, or something?
I'm also wondering about conjectural aircraft. A DH10, O/400, or Gotha could have lifted a torpedo, but I am not sure they would have been practicable torpedo bombers. As I understand it, if a plane has a 100' wingspan then it can't manoeuvre at altitudes much less than about twice that. If it tries to the wings will hit the surface or ground when it turns, so to use a large aircraft to drop torpedoes you need a torpedo that can stand up to being dropped from relatively high up. Is that about right?