oyviv
As a retired senior detective and AVSEC specialist, I laugh when somebody says they can't spot too many, sleepers in the PAX manifest.
If it were as easy to catch hijackers by reading down the PAX manifest, we'd catch them all easily.
Hijackers don't necessarily have the same profile as your average terrorist. Why? Because not all hijackers are terrorists.
As for the crew, the captain and first officer have nothing, it seems, in common. There is a large age gap. There is a large disparity in experience. One appears to be a man dedicated to his job, the other a bit of a playboy (if earlier reports are at all accurate).
And no one planning this type of op would have drawn attention to himself by publicizing that he had a fairly good mock simulator in his house.
If the aircraft has been nicked, its more likely to be via hijacking.