Andu:
There are some airlines... well, one... and a rather large one at that, where it would have been impossible for the captain to return to the flight deck in the situation the AF447 found themselves, because, impossible as it might seem, the captain's crew rest bunk is even further away from the cockpit than the length of the aircraft!!!
I'll let the cat out of the bag:
It's above the cabin ceiling at the aft end of coach.