The chapter of Mahon's book on the CAD (at p98) contains yet another example of his irrational fear of "active volcanos". I'm wondering if this has something to do with his being from Christchurch (although I know several people from Christchurch who have managed to cope with a visit to Mount Ruapehu).
Having noted Mahon's paranoia, the Auckland-based union lawyers, who probably spent half of August at Ruapehu, structured the evidence accordingly. And so it transpired that Capt. S. would have screamed blue murder if he had known that his nav track went over Erebus. Strange, then, that he thought it was unusual when it didn't.