Yeah I went skydiving in 2000 - wasn't long after I got diagnosed, so I think it was my dad's consolation present for that. :p To be honest I never even THOUGHT about the risks of hypo at the time... but on thinking about it, I guess if you make sure you eat just before you go, something low GI like a sandwich, and then maybe have, say, an apple before you go up in the plane, you should be pretty right. Probably a good idea to get your sugars up a little higher than normal, even, because once that adrenaline kicks in it could lower them a bit.
Whatever you do, have a great time! :)