The end of 9/11 happening again occured right in the middle of 9/11, with UAL 93. Passengers figure out it's not a hijacking they might survive, and that you'r

The end of 9/11 happening again occured right in the middle of 9/11, with UAL 93. Passengers figure out it's not a hijacking they might survive, and that you're going to crash the plane into a valuable target. Then, having nothing to lose, they revolt and ruin your plan. So that particular type of plan isn't going to work again. Passengers no longer assume "hijacking I might survive".