Has there ever been an aircraft which was hijacked solely because the cockpit door, though locked and physically sound, was too easy to unlock?
Any cases?
Whereas there are well over 100 people dead because a cockpit door lock would not open.
Double pilot incapacitation - is there a pilot aboard? There was. The cockpit door is supposed to open if someone rings a bell and neither of the pilots overrides the door opening in 30 seconds - how else could double pilot incapacitation be handled?
Except that it was a code pad. The purser was incapacitated as well - and the purser alone knew the code. 2 pilots and 1 purser incapacitated was enough to doom everyone aboard.
The door eventually did open - when the fuel was exhausting and engines started to flame out, the lock was unpowered. But it is one thing to figure out the way to land a 737 with PPL and quite another thing to figure out the way to do deadstick landing.
So... write down the damn code and place it so that it can be seen. At worst, you have to push the override button every 30 seconds and less.