I've never hired a plane for aerial photography, so whenever I fly, which isn't very often, I am looking for opportunities to shoot out the window. Of course, you need to have a window seat. And not a window seat over the wing! Focus in not a problem (although the window needs to be fairly clean and not fogged) just set it on infinity and leave it there. 1/100th of a second or faster is good in case there are pesky vibrations. I put the lens right up to the window. Frame up as best you can and shoot. Photoshop helps with the white balance as airplane windows usually have some kind of tint. Sure, a small plane with an open window would be better, and some day I will probably try that. But for now, I am well satisfied with what I can get.