Originally Posted by
jafa
1. Suppose there was one of these low tech curved metal gadgets, keys we used to call them, overrides the number code pad, when you go out of the cockpit you take it with you. Having a system which can, through malfunction or otherwise, lock people out of the cockpit was always going to cause grief one way or another.
The problem with a physical key, as with a keypad, is that the door has no way of knowing whether the person trying to gain access is a genuine crew member or a terrorist who has obtained the key/code under extreme duress.
It follows that the cockpit occupant(s) need to have the ability to unconditionally block access, if necessary. Making sure that decision is made by two people rather than one is probably the best we're going to be able to achieve.