Actually, I disagree. The hijacker(s) should be attacked until they stop resisting. If they're still alive at such point, belts can be used to restrain them. By killing them, you give them the martyrdom they want. By keeping them alive, they may be able to sing for an interrogator.
Having them dead may be satisfying but alive they're of much greater intelligence value.
Do we need a "brig" on each aircraft to keep prisoners alive until they are interogated?