Following a history of airline hijacking and bombings very nearly as old as airline transportation itself, Al Qaeda has managed to frighten airlines and various federal authorities into instigating a string of measures so draconian that it's hard to keep track of the human rights and logic violations at work.
But, it seems that it could, after all, be worse.
According to the highly entertaining History Without the Boring Bits, in 1972, Jack Jensen, of Fort Worth, Texas (surprise, surprise) suggested installing a hypodermic syringe underneath each seat, allowing hijackers to be injected with a disabling or fatal dose of... something, at the pilot's discretion. Airlines allegedly decided that passengers wouldn't be able to relax, and decided not to adopt this system.
We also have the problem that, quite apart from putting that authority in the hands of the pilot... Don't most terrorists stand up when they start with the whole announcing-themselves-and-making-demands schtick? Particularly if they know about counter-measures like that?