I have followed the whole thread with interest. Metro man raised a point that I have been waiting for:
"The cockpit door seems to be the big factor in all this ,so let's do away with it. Weld a big piece of steel from one side of the aircraft to the other , that would require a cutting tourch to get through ,bit difficult to get one past security. Have a letter box system for passing meals through. Crew to enter and leave via emergency exits. Access to the flight deck impossible from the cabin, ever. Problem solved."
We then got folks saying what about the toilet? Well, they can have one their side of the bulkhead. Food is through a double doored single access hatch as suggested.
The problem is that, doing so will take more space out of the cabin and then less room for all those lovely pax that you are all so desperate to protect! Placing a full bulkhead between the FD and cabin is the only way to prevent access.
However ... the next attempts at serious terrorism are unlikley to be aircraft. There are ships and trains and all sorts of fun and games they can have. Each event will cause more stable doors to be shut after the horse has gone.
Yes, there will be some attempts at a/c hi-jacking but I doubt if the big boys will bother for a while.
Guns on the flight deck? No. Not the answer.