@prospector - The DC-10 had a theoretical maximum capacity of 380 passengers. Even if we knock some off so it's not all cattle-class , you're looking at about 330-350, which leaves 103-123 seats free from your stated number of 237. It was deliberate policy to "underbook" the Antarctic flights because to fill the central rows would impede cabin movement, as I said, and there's no point in going on a sightseeing flight and sitting in the central row!
The DC-10 may not have had the carrying capacity of a 747, but it was still a sodding huge airliner!
@chris_lz - No I wouldn't, but let me think about it a bit.
@ampan - Let me do a bit of digging to check. First thoughts - "him" could refer to the controller, but the transponder could still be coding.