Its highly unlikely for my POV, that the passengers augered the plane themselfs. Think about it, there were 5 armed with knives against 60 angry passengers.
This is the scenario:
1.theres 2 men in the cabins, 3 in the back guarding the passengers.
2.Passengers attack after negotiating it with amongs themselfs.
3.3 guarding hijackers maybe stab one or two, but are eventually knocked out and prolly killed (i would twist hijackers neck if i were them)
4. other of the "pilots" see whats happening and close the cabin door.
5.They do the only thing they can and push the nose down, intended crash, very likely pre-issued plan B.
I think the passengers never reached the pilots cabins, the pilot knew they wouldnt make it to the target. Muslims go straight to paradise when they commit suicide in holy terrorist act like this, so it wasnt hard decision for them.
Remember, these preparations took several years, they were fully teached how to act in different kind of situations.
When youre hijacking plane with swiss army knives, you can be very certain, that problems may occur and they knew it.
