The passengers of the fourth plane knew that other planes had been hijacked and crashed that same day. They made the assumption that these multiple hijackings in such a short period of time were all related and concluded that their plane would likely crash.
The probability that a random hijacking would be done with the intent of crashing the plane is far lower in general than on a day where you know another 3 hijackings did result in that. Especially when you consider how unlikely simultaneous hijackings are.
The probability that a random hijacking would be done with the intent of crashing the plane is far lower in general than on a day where you know another 3 hijackings did result in that. Especially when you consider how unlikely simultaneous hijackings are.