Cabin crew.
Whilst we may consider the actions and motives of the flight crew, what about the cabin crew - have they been considered.
I'm cabin crew, with a ppl, and an interest in aviation. I know the basics of flight. I believe I would be capable of altering the auto pilot coordinates. I'm certain that I could not land a B777 without considerable training. Maybe one of the crew thought they could?
Importantly, as a third party hijacker, I know exactly how to enter the flight deck and would my request would not raise any suspicion. Particularly if I'm equipped with two cups of tea at the top of climb.
Just, another, thought