In the decades before September 11, there were hundreds, perhaps thousands, of airline hijackings. Most were not hijacked by religious fundamentalist terrorists, and very, very few resulted in any violence. Four related hijackings on a single day probably aren't going to change that, other than if increased security or the perception thereof stops a depressed immigrant, possibly with mental health or drug or whatever problems, wants to "go home" and sees an airplane hijacking as the best way to get there.

The probability of a repeat performance is no higher now than it was on September 10, and is probably lower with heightened security activity and awareness, and increased law enforcement activity. As well, the element of surprise is gone.

But the next time there's a hijacking it might be a huge mistake to presume that the plane will be diverted into a building. It's not inconceivable that more people with be injured or killed if the crew and/or passengers over react.

But each person will have to carefully evalute the situation, should the occasion ever arise.