NOTE: If you have security concerns,please respond with private message. Hijacking 4 airliners on 9/11 required a helluva lot of planning - especially as to "flight plans". It might have been "relatively simple" to hijack the planes ,and, since some of the hijackers had taken lessons,they could operate aircraft controls to some degree ; but how about the navigation? Think about it for a minute.You take over an aircraft,but cannot reliably predict how long the takeover efforts will require,and what your location will be when this occurs. You now have to change course and altitude precisely so you hit your...