It's entirely possible it's not the right course of action, but it's reflex. Now that it's known terrorists view aircraft as weapons, even taking control of the

It's entirely possible it's not the right course of action, but it's reflex. Now that it's known terrorists view aircraft as weapons, even taking control of the aircraft is a deadly threat. The weapons usually used to control an aircraft are the threat of bombs. A fake bomb is just as effective as a real bomb, and vastly easier to bring onboard, so it seems rational to presume any bomb threat is fake. To a first approximation, hijacker in a plane aisle is a problem of running at him and tackling, which is about the easiest possible thing to do.