Perhaps I should have said that they could use the autopilot/FMS to get themselves in the general area of the WTC or Pentagon. and then hand fly in the final phase - we're not talking about finesse. I'm not suggsting that this was the case just saying that it is possible.
On another point, I've done one of the these VIP (perk of being a journo) things at braincrank with the said hand flying around Manhattan and the WTC (744 sim) and frankly in the light of yesterday it was disturbingly easy (for a GA type of driver). I accept that with a clearly well researched attack the perps may and indeed, hopefully (since it may help in tracking them down) sought some kind of professional level training.