Originally Posted by
iluv2fly
Unnecessary, because on this route, there are four pilots on the flight deck, so if one comes out, three still remain.
AFAIK, the two crews are not "on duty" for the whole of the flight and do change sometime during the flight... I do not believe the four of them are in the cockpit all the time... After all, there is not enough space for four of them... I have actually been to the cockpit "en route" and there were only two people (aside of me) on the deck. And before you ask, yes, I have proper clearance to be on the flight deck during the flight...