[Pearls Before Swine]

I think it was the pilot. He killed this guy and then climbed up to kill the passengers.

Question: When the pilot or co-pilot need to go to the bathroom, do they exit the flight cabin?

If the answer is yes, that's the time to lock the door and climb.

[Viennacon]

Yes, they exit, and yes, they can be locked out.

[plain talk]

They would not need to go to bathroom one hour after the flight takes off. Certainly the plan could not be dependent on waiting for someone to take a leak. Not enough fuel for that nonsense.