in 1994 Algerian terrorists hijacked a french airliner and threatened to crash it into the Eiffel tower. However they werent trained as pilots and could only try to force the pilot to do their bidding, which of course would not work as any pilot would do their best to avoid crashing into buildings.
(eventually french commandos stormed the plane on the ground and killed most of the terrorists)

There was a hijacking incident in Africa in the 90s where an insane man attempted to crash the airliner - the pilot and copilot eventually overcame him but it was close.

the suicide bombing concept came out of Lebanon in the early 80s devised by the Hizbollah as a tactic against Israeli and US targets.

so to put all of these elements together should not have been that difficult - the US has terror think tanks whose job it is to come up with scenarios and work through various responses.


a terror analyst in Vancouver very accurately predicted the idea of using hijacked airliners as missiles before 911, he was even investigated by the CIA afterwards.