Why Osama pulled it off

[TaiDaishar]

The armed pilots would still have likely been trained to cooperate with terrorists and avoid casualties.  After all, it's not like the passengers themselves are unable to overpower a few boneheads with box cutters.

I doubt that this "policy" was the thing which prevented the passengers of taking over the plane, most likely was that they simply waited their lives off for someone else to be the hero.

Oh and in 9/11 there was another airplane that was most likely taken by the passangers and even though didn't succeed to land safely at least didn't crash on another building that would've killed dozens, hundreds or maybe even hundreds more lives.