What if... what if the plan was to have a passenger or flight attendant check out the lavatory? The person sees a thread and stupidly pulls it - Boom! Or they turn on the water or wiggle a loose piece of wall or pulls on the tp or whatever and the terrorists try to justify their innocence to Satan in that they weren't the ones who blew the plane up?
That makes no sense. Why would they go through all the trouble of putting together such an elaborate plan and then rely on dumb luck for its completion?
In any event, terrorists have no guilt about what they're doing. In their minds, they're doing God's will.