Well, I did hear that the hijackers plan was to slit the throat of one passenger, in order to keep the rest in line. Not sure if that happened or not. The other thing is, we have been programed to not be confrontational when put in a situation like that. Nobody knew what the plan was (ie flying them into buildings), so nobody on the plane had cause for concern. Similar to what happens if you are in a bank during a robbery. Just sit still, stay quiet, and when the towel heads have their money, then you will be free to go home.