Does anyone know the name of this movie? Its a horror movie from the 80's or 90's.?

I only remember a few things, so if someone gets this I'll be impressed and thankful. It's about a guy that at some base I think where he gets maybe some sort of experiment done on him and he becomes crazy. He ends up losing his hair and I think his mouth gets big too. I remember a scene where he jumps out of an air vent onto someone and kills him. I remember seeing that shot on the back of the vhs cover as well. I think at the end of the movie the crazy/mutant guy chances a plane when the people are trying to get away.