He may not be able to carry a fixed blade. He would have to talk with his CO about it.
As for a folder...he can order automatic knives and he should be getting one issued or given money for one.
If you get him something, make sure it's a quality company, and more importantly high end materials. ( Benchmade, Spyderco, Combat Elite, etc...)
If your life depends on getting the hell out of the bird fast...you want a $20 chance? Or a quality knife you can use without any doubt of it performing?
Don't forget he may need a knife he can fight with. There's a reason he has to go to S.E.R.E. for his MOS.
As for a cutting tool...Benchmade (among others) make a safety cutter just for seatbelt/harness strapping.
http://www.benchmade.com/products/7
I'm not too familiar with knives that have the cutout in the handle for strap cutting. I've used them, and they aren't as good as a safety hook or open serrated blade.
If you wanted the best of both worlds...get a folder with at least a partially serrated blade.
Sorry I couldn't be more help with a specific model. And I don't mean to sound like a D bag...but, what if he doesn't like what you pick? Guys are VERY picky with their knives...especially if your life may depend on it. I won't even buy a knife made from certain steels regardless of brand.
Personally if I were you...I'd just get the safety hook. It's something he would attach to his vest and pretty much never take off. Always there, always in the same place. Good thing for something you may have to use while upside, disoriented, and wounded.
I hope my insight helps, and again...no disrespect intended