Secure Door Hijack Scenario
Martial arts trained bad guy in front rows of business class waits for a pilot to exit/enter cockpit via secure door -- entering cockpit is better because bad guy can attack from behind.
Bad guy jumps pilot at door, knocks him aside, enters cockpit, closes secure door, does in remaining pilot.
F-16 only way to counter hijack.
A secure cockpit door is only half a solution -- you must also have a secure door to the front galley and an interlock so that the cockpit door will not open when the front galley door is open in flight. The front galley area must be secured pax whenever the cockpit door is to be opened.