Fortified Flightdeck Requires Double Door
Capt. Crosswind: Fortified is good as long as a martial arts trained bad guy can't jump a pilot coming back from a lav break, close the door behind and take on the remaining pilot, likely before he even gets his hand near his weapon, let alone use it effectively. With a single fortified door, this scenario can/will happen someday -- then we'll put in double doors with an interlock.
And the other problem with weapons is that your own side gets killed much more than the bad guys. Gun accidents kill far more family members than iintruders.