Maps
I don't think I missed H'snort's point re a map. Yes, a map won't help if the sector whiteout prevents you seeing anything. But this wasn't the case. Although the crew couldn't see Erebus, they could see Beaufort Island. If you knew where you were in relation to Beaufort Island, then you would know where you were are in relation to Erebus - if you've got a decent map. If you haven't got a decent map, then that island down there in the sea is just an island down there in the sea.
Does anyone know what maps they had on the flightdeck?