Space Fighter Game

I need some help with this project I'm working on. It's a simple space game in need of a lot of work. Could you guys post suggestions and what you think of the game. Also there seems to be a bug I haven't pinpointed yet that I'm still working on, it makes the game crash and I think it has to do with Health changes. Here's the controls:
Up= Turn Forward
Down= Turn Backward
Left= Tumble Left
Right= Tumble Right
A= Move Forward
Z= Move Backward
Space= Fire Weapon