I believe it was no coincidence, that the bastards of 9-11 only hijacked Boeing 757/767 models. That time, there was on commericial add on for the Microsoft Flightsim available, which had a functioning layout (including FMS, Autopilot systems) of a Boeing 757/767. No other software at that time was so advanced than this particular program.
To do what the hijackers did, doesn't require a lot of flying skills. We are not talking about V1-Cuts, Decision making, Hydraulic failures, Landings... They only have to program the FMS and dial some switches on the Autopilot. With the 'training' on the 757/767 Software Add-on and a handheld GPS a piece of cake.