Another thought on the environment and equipment choices. There will be a fair amount of vibration. Airplane engines are basically non-muffled. They have mufflers, but I saw the insides of one once and it was basically hollow with a few baffles (and cost, like $500!!!). The level of vibration will be like driving down the road in a car with an unbalanced tire.
So, fast lens, fast film and fast shutter speeds seem in order. I know the Leica R6.2 goes up to 1/2000th. The R6 tops out at 1/1000.
Others can help more than I in this area. I shoot LF at small apertures and nice long exposures so I'm in a different world.
Also, I'm wondering if 50mm is going to be enough. Depends on the altitude and how much he wants to take in. If he is photographing top-secret military installations or trying to catch Bush sunbathing on the roof of the White House, I would think he would need some long lenses, too which just makes the vibration issue worse. How about a glider? Zooms would be nice, but a fast one costs a mint.
Can anyone suggest a long lens that is also fairly fast and not too much $$?