mainly just situations where I'm powerless to influence the outcome.
I have a lot of self confedence, or at least if I'm actively doing something I can put the problem out of my mind.
for example, I don't have a problem with planes but sitting in an airliner being flown by a guy I've never met, and can't see requires some alcohol. I actaully think I'd be more comfortable with flying it myself even though I'm completely unqualified (flight sim experience aside.

same thing with the idea of skydiving. it's not the idea of the alt, the falling, or the fear of death. it's the thought of having a failure, running out of options and waiting to hit the ground. the thought of those powerless moments is pretty damn terrofying.
when things go really wrong I'm actually quite level headed, and can deal with just about everything life has thrown at me so far. it's afterwards when everythings ok I usually have the panic attack.
in case you haven't guessed I'm kind of a control freak.