I'm not a great fan of being near cliff edges etc. I wonder whether flyers find it easier to cope with heights when flying because they are sitting down and thus unable to 'fall' anywhere? I can look over a cliff edge no problems if I lay on my stomach and look over. I know I'm not going to fall then.
I must admit, flying has never bothered me much, whether doing aeros, low level in choppers etc. I think the only thing that bothers me about flying light aircraft is a mid air. I've always flown gliders with a parachute and I feel slightly naked not wearing one in a light aircraft. I know you can argue about the chances of getting out etc but logic doesn't count for much when you talk about fears.
I have heard that really high altitude flyers, spy planes and the like sometimes get the feeling that they are balanced on a knife edge and the plane will topple over at any moment.
My phobia is deep sea. I'm a strong swimmer, love swimming in the sea but I won't swim in the ocean, as in really deep ocean. Don't know why, it's one of those primeval things, there's stuff lurking down there you know.......