These are my thoughts as well
Apparently in the US airlines are required to have 2 people in the cockpit at all times. If the captain has to use the bathroom, a flight attendant goes inside until he returns. I also commonly see them block the cabin door with the food cart when this happens but I'm not sure if that is SOP. However, in other countries they don't have this rule, so apparently it wasn't a violation for the copilot to be alone in the cockpit. I suspect this rule will become a global requirement if it is confirmed that this was an intentional act by the copilot.
Also, if you watch the video that was posted, it seems there is an override for the door that is activated from the cockpit. The pilot can get in without assistance via a passcode, but he can also be locked out from inside, passcode or not. Having 2 people there would help to mitigate this risk, but in this case we know there was only one person. Also, the lockout for the door only works for a timed 5 minutes, then it would have to be pressed again. This seems to indicate that the copilot was conscious and this was intentional, because otherwise the pilot would have been able to gain entry 5 minutes after one attempt to keep him out, or an accidental pressing of the lever and a subsequent medical issue (e.g., unconscious copilot). There are audible buzzers when people enter the code from outside, I'd be curious to hear if that was on the voice recorder and what it tells us.
The buzzers, in conjunction with the flight data recorder (if it logs the door and lockout activity) will be very telling as to what happened. If you hear the buzzer from the pilot entering the code multiple times, and the lockout lever is pressed multiple times, I'd think we can draw a pretty firm conclusion that this was intentional.
Edit - BTW, I think the buzzer audio indicating a door code was entered is absolutely vital. What if nobody on board, including the pilot, knew the passcode to the door? This is one scenario where I could imagine a tragic accident. The pilot leaves, the copilot starts a descent for some valid reason and passes out immediately thereafter. Now the copilot is unable to change the flight path and the pilot is locked out because he doesn't know the code. Extremely rare likelihood, but a possibility.
This post was edited on 3/26 12:25 PM by PSUSignore