With 9-11 the terrorists violated a social contract. It used to be that in a hi-jacking the terrorists had a beef with one govt or another and there was a good chance that you would simply be inconvenienced for a day or two. that contract is now null and void. Richard Reid was the first to find that out.
One person might feel intimidated, but in a group, an otherwise timid person is going to feel a little more courage. Add in a person or two like me that are a little high strung already, a couple of wannabe heroes, a few athletes aging or not and you have the makings of a little big horn.
When do these folks figure out that once they crash into something they are no longer here nor there to make a point to anyone. I still don't understand why they are so bent on that. The recruitors for these missions must have one hell of a line.
One thing that I have noticed is there are a lot of people who talk big, but when it comes right down to the nitty-gritty don't do anything but bite their nails waiting for someone to do something.
Like I said there were most probably people on that plane who said the same thing you did and then did nothing.