What's likely caused hijackings to fall off a cliff is a) reinforced cockpit doors and b) the knowledge of crew and passengers that the hijackers might be homicidal.
Pre-9/11, advice was to cooperate, get the plane on the ground, and negotiate/assault, with pretty good overall results for the passengers. That is... not the advice today.
Reinforced cockpit doors were not implemented on planes until around 2002. Meanwhile, hijackings fell dramatically after only basic fight security that was implemented nearly 20 years before that.
The TSA reliably fails penetration tests; they miss between 70% and 95% of them. https://www.forbes.com/sites/michaelgoldstein/2017/11/09/tsa...
What's likely caused hijackings to fall off a cliff is a) reinforced cockpit doors and b) the knowledge of crew and passengers that the hijackers might be homicidal.
Pre-9/11, advice was to cooperate, get the plane on the ground, and negotiate/assault, with pretty good overall results for the passengers. That is... not the advice today.