No one will ever hijack a plane again anyway. On September 10, 2001, everyone assumed that if a plane was hijacked, its passengers were kidnap victims who were likely to be returned.

That assumption has been completely thrown out of the window. Now the assumption is that everyone on the plane is going to die, and there should be enough numbers for there to be enough people able to overcome their fear and overwhelm the hijackers. Assuming that the stories are true, this is exactly what happened on United 93, and I'm sure any potential hijackers are well aware of this. There is no longer any possibility for a successful hijacking without the first step being the disabling of all the passengers.