The hijackers chose Boston and the NE US. I bet they considered that they would encounter less resistance than if they’d took one out of Dallas or a Southern state. But there are always “what ifs” to be considered.
One has to remember that passengers believed there was a bomb on board and the terrorist o9nly wanted hostages to bargain for their (presumed) demands.
It was only on later flights that they knew what we knew they were intent on suicide mission. It was on Flight 93 over Pennsylvania that Todd Beamer and others took action and said those memorial words..
“Lets Roll.”
From then on to today, nobody would think twice about taking on anyone who dared endanger their lives on any flight...