Another poster saw no difference between this flight crew member and a terrorist
in many ways he is correct, both through their actions one a badly disturbed mind the other radical religious beliefs have carried out evil deeds with similar consequences.
The door designed and placed there to protect the flight crew from intrusion by a terrorist has worked in the opposite direction by allowing a flight crew (terrorist) to refuse entry to the Captain who could have saved this situation had it not been for the door.
There was probably little perceived threat that the terrorist would be within and the door systems were designed around the fact that the terrorist would be outside the flight deck in the cabin.
This act has highlighted a demonstrated threat and as with all demonstrated threat the authorities have to minimise that risk.
that demonstrated threat has shown that terrorism can and has worked both ways so the system has to be redesigned to take into account a threat from both directions and this is probably the biggest lesson to learn from this awful crash not so much the nature of the terrorist whether radical religious or disturbed flight crew. We are talking about the same thing! A terrorist on an aircraft.