Some of my relatives just got home from a vacation. They were in first class, and they were very concerned over the cockpit access. Basically, when the pilot opens the door, a flight attendant stands in front to 'block' access. Obviously, this wouldn't work very well if someone wanted to get into the cockpit.

Now, I'm all for reasonable security measures as much as the next person is. But this seems like it might be a plausible (if unlikely) threat.

Thoughts?