So potentially the older faster primes are going to be a non starter - any thoughts on the cheapo 55-200 ?
The old non VR 55-200 has reasonable resolution for the price, its a bit cheaply constructed, so don't batter it around.
Its going to be a struggle as far as AF and shutter speed, a slow aperture and limited ability to use high ISO settings before noise becomes a problem.
It sounds like the best compromise for your buck, a manual focus lens might be pretty frustrating for flying aircraft, but for those on the ground, it should be easy. Just make sure he keeps his shutter speed to 1/250 or more when zoomed out.
A rental of a faster lens might also be something to consider, but it won't be cheap either.
Here is a review. http://www.photozone.de/nikon--nikkor-aps-c-lens-tests/245-nikkor-af-s-55-200mm-f4-56-g-ed-dx-review--test-report