I think that all this talk of locked, bulletproof, security doors has overlooked one point. What happens when the crew need to go down the back for a pee??? The hijacker need only wait serupticiously at the flightdeck door after taking control of the cabin. I believe the only aircraft with a loo directly accesible from the flightdeck is the 747-400? So then, is the mod programme for thousands of aircraft going to include an entire new toilet installation as well as the "impenetrable" door??? I believe the best solution is (unfortunately) a semi automatic pistol on the flightdeck with a Captain who is not afraid to use it. Even this has its problems, day to day security of the weapon itself, and effects on the aircraft if it was actually used.