Gentleman Aviator and the Commander
Both with absolutely sound ideas. The Flight Deck door should remain closed for the whole flight. If we wish to stop the same type of incident happening again, then this can only be done by making the Flight Deck door totally secure and it be physically impossible to gain access from the cabin during the flight. As pax will always be able to smuggle things onboard or grab a fire axe or heavy fire extinguisher, or take on board chemical incapacitant sprays, weapons must be considered to be available to these peolple. If we go down this route, which is the ONLY way to prevent similar incidents, by stopping them physically getting at the controls, then there will have to be major changes to the inside of the aircraft - lavatories, food, additional comunication between FD and cabin, operational procedures - all of these and more, will be topics to be discussed.
A very, very, very sad few days for us all.