Did you see the movie Con Air? They had everyone handcuffed to their seats and chained at the ankle, but still the bad guys won control of the airplane. Only a movie, yeah, but who would have believed in the attack on the WTC if they had not seen it live?
If a fellow stands up and claims to have a bomb, flight crews are required to take him seriously. So it is not necessary to smuggle anything on board.
We should be looking at what to do WHEN it happens, and back off a little on the airport security, lest there be no passengers to protect.