More comprehensive pre-flight screening could not have stopped the Sept. 11 attacks, because they did not involve sneaking contraband onto the plane. The cardboard box cutters that were used in the attack were allowed at the time.

Yeah but the Israeli style behavioural profiling very well might have flushed their intentions out.

Exactly. This is a perfect argument for the Israeli style of behavioral profiling as opposed to the American style of trying to imagine every possible way to hijack a plane.

It might have, but surely not to the level of certainty that your GP suggested.

That's why, apart from pre-flight screening, they have a policy of having plainclothes air marshals on every flight and locking the cabin door.