>Until 9/11, there was never a plot that involved intentionally hijacking an airliner with the intent of using it as a weapon and killing everyone on board.
Fedex Flight 705 (7 April 1994), before 9/11. Pilot tried to kill other pilots so he could crash plane into FedEx hub and destroy it and employees. Was subdued, barely, by a pilot with cracked skull that then managed to land the plane.
Egypt Air 990 (31 October 1999), before 9/11. Pilot deliberately killed everyone on board, thought it wasn't a weapon.
Fedex Flight 705 (7 April 1994), before 9/11. Pilot tried to kill other pilots so he could crash plane into FedEx hub and destroy it and employees. Was subdued, barely, by a pilot with cracked skull that then managed to land the plane.
Egypt Air 990 (31 October 1999), before 9/11. Pilot deliberately killed everyone on board, thought it wasn't a weapon.