I don't think your average terrorist understands that calculation, so by brandsihing a knife, thinks he's in control.They are clearly counting on suprise to mollify the passengers.But the outcome was going to be same, no matter, and that was because of the lack of armed weapons.Do you understand what I'm saying here? Does it make sense to you?
I do understand, but I believe you are oversimplifying it. It is a fact that most hijackings do not result in mass death...the crew would incorporate this into their response and into the advice they give the passengers.
In this instance, it was tragically wrong. The people on the 4th plane had information that the people on at least first two planes did not. Therefore, the decision was decidedly different for people on that plane...they knew that this particular hijacking was NOT likely to end on a tarmac somewhere. As a result, they took action.
Thus, IMHO it is unreasonable to posthumously criticize the passengers on board the other planes. It is a natural reaction to a devastating event, but it is not rational and does not take into account the likely state of mind of people on those planes.