You're all so worried about various methods of locking that stupid door, one way or another. It is irrelevant. Here is why.
Can anyone tell me how many attempts there have been at forcing a door open so far???
I have never heard of one. The door in every case was either not locked at all or opened by the crew themselves (obviously as a result of threats from terrorists).
So no matter how good your lock, the terrorist will convince the crew, one way or another, to open the damn door or else...