What the 9/11 hijackers took advantage of was the “common strategy”, common that is to all US airlines. The common strategy was to cooperate patiently with the hijackers and wait for military or law enforcement to deal with the situation. There’s a lot to be said for this but the real reason for the common strategy was legal liability.

The common startegy only lasted for about an hour into the suicide era, as the passengers and crew of United 93 realized fighting back was the only chance they had. I don’t think hijacking an airplane would be possible anymore, even if you didn’t intend any kind of suicide mission, because you would be swarmed by enraged, terrified passengers.

The 9/11 hijackers knew very well they would be cooperated with and given access to the cockpit so that part of the operation didn’t require much bravery. As for the rest, it’s for others to debate whether committing suicide is a brave act or not.