Originally Posted by
pueywei
There is no information avaliable (to us, at least) that proves that the pilots were incapacitated before they brought the plane to their final destinations. They could very welll be attacked after they were just about done with it.
Read the report:
http://www.9-11commission.gov/report/911Report_Ch1.htm
There were numerous phone calls made from the plane by passengers and FAs which led to the conclusion that the pilots were NOT in the cockpit. Also, the unauthorized altitude excursions of all of the hijacked aircraft which followed the time of the suspected takeovers would also lead to the conclusion that the pilots were no longer at the controls. Also, keep in mind that the CVR from UA 93 was recovered. They know exactly what was said in that cockpit word for word.
Still the greater point is not whether the 9/11 hijackers could have navigated without GPS assistence. Sure, it is possible. But I suspect that they might have used portable GPS devices that were pre-programmed with their targets.
But as has been pointed out recently, GPS capability is integrated into so many devices now that it would be impossible to stop without banning all electronic devices from the cabin altogether! The Brits kind of tried that for a few days last summer, but the airlines did not like checking laptops for a moment!