After the crash of Air New Zealand Flight 901 with loss of all aboard on 28 November 1979, New Zealand's official accident report was released by the Chief Inspector of Air Accidents, Ron Chippindale, which cited serious pilot error as the chief cause of the accident. Public demand led to the formation of a Royal Commission of Inquiry into the accident. Mahon produced his report on 27 April 1981, which cleared the crew of blame for the disaster and found that the major cause was the reprogramming of the aircraft's navigation computer without the crew being notified. Mahon claimed that Air New Zealand executives had engaged in a conspiracy to whitewash the inquiry, covering up evidence and lying to investigators, and concluded that they had told "an orchestrated litany of lies". His book, "Verdict on Erebus", an account of his inquiry, won the New Zealand Book Awards prize for non-fiction in 1985. Mahon retired from the High Court bench in 1982.