hell yeah it should be. If the passengers on the Sept. 11th flight had guns to shoot the terrorists with, we'd be saved 3000+ lives. Of course this would be up to the airport's decisions, but it should be legal considering the lives of the passengers is at stake.
Wouldn't it be quite easy to make the plane crash by shooting through the walls or into the cabin or something?
I think they've actually done studies that prove that is bunk.
I love movie fiction, like the movie Goldfinger, where Goldfinger shoots a hole in the window, and it's a tiny window, but he gets pulled through and he's obviously not the most slender guy. Yet James Bond is standing there and he doesn't fall through.