As a brief follow-up to my comment on the September 11 atrocity, it could well be that some of the passengers of UA flight 93 (the one that crashed in a field rather than into a building) did indeed act with selfless nobility to try to prevent deaths on the ground. Alas, they couldn't save the plane — by the time the terrorists had control there probably wasn't much chance of that.

This kind of selfless attitude — putting the safety of others above one's own — will be the only effective defence against this breed of terrorism. If people resist terrorists before they take control of the plane, then there may be casualties, but it can't be any worse than the results of letting the terrorists gain control. In the worst case scenario where the passengers and crew resist, the terrorists really do have a bomb and the plane gets blown up. This is still preferable to the plane being used to attack a ground target, and no worse than what happened to flight 93.

More importantly, if terrorists know that the pilot and crew will refuse to relinquish control of the plane at all costs, that makes planes an unattractive target in general for terrorists. Will we actually see a policy shift in dealing with hijackers as a result of this event?

BBC News has a more detailed report of the known events on UA flight 93.