I know that Swissair has an armoured cockpit doors on most of there aircraft. They also have a video camara looking back into the area immediatly behind. That keeps the cockpit crew more or less safe and they can see whom is coming or trying to get on to the flight deck. This certainly does not solve the ultimate problem. And, that is, how to screen boarding pax in a more efficient and practical manner? The other part of the equation, is how do we combat terrorism or even solve the worlds problems. I am sure that this issue will a discussion point for many years to come! In the mean time my condolences to all whom have been touched by these tragic events.