There was a thread a couple of months ago (sorry, I cannot find the URL link for it, the search function on PPRuNe won't work cause the server is too busy) in which it was almost unanimously concluded that anyone who was a good performer on Microsoft Flight Simulator etc. but who was not a trained pilot would not be able to land a modern airliner.
The kinds of manoeuvres that these planes went through indicates something beyond amateurism in my opinion. The flight paths of the high-jacked planes, and the fact that all three of the successfully high-jacked planes precisely hit their targets leads me to believe that all of the teams of high-jackers contained one of more pilots with the following alternative backgrounds:
1. extensive 757/767 type simulator training on top of basic flight training.
2. civilian aviation training and operations, probably with 757/767 experience;
or, most scary of all
3. military aviation training.
The whole level of sophistication of this horrifically successful operation suggests something beyond a bunch of simple religious zealots practicing flying on their laptop computers out in a guerilla training camp in a remote part of Afghanistan.