The Erebus tragedy would never have happened if a Civil Aviation inspector, scheduled to be on board that day, had made the flight.
That's the conviction of Maurice McGreal, a former pilot and Civil Aviation expert involved in the Erebus inquiry 30 years ago, and still acutely interested in what caused Flight 901 to smash into the bottom of the mountain on November 28, 1979.
The day of the doomed flight, Jack Spence, a Civil Aviation DC-10 inspector, was scheduled to join the sightseeing flight to Antarctica. Instead he asked McGreal, then assistant director of flight operations for Civil Aviation, if he could go on the next flight because a family member was ill.
McGreal agreed, a decision that he and the late Jack Spence would come to regret.
In McGreal's mind, the pilots on Flight 901 would never have flown so low without clear visibility an aviation "no no" had Spence been on board.
McGreal, now 91 but sharp as a tack, all but dismisses the infamous computer navigation error, programmed into Air New Zealand's ground computer, as a red herring.
"Flying is a dangerous business. If you don't know where you are, you have to stay at an altitude above all obstructions until you do."
In McGreal's living room, among a pile of Erebus papers and clippings and a hand-typed copy of Ron Chippindale's Air Accident Report, is his biography, A Noble Chance, which he wrote 14 years ago. In it McGreal says that "no pilot would have displayed before a Civil Aviation inspector such a poor level of airmanship".'
While the passengers, who had paid handsomely for what was a sightseeing flight, "might not have seen what they had hoped they would see, they would have lived to tell their children of their unique adventure ..."
Keith Amies, a DC-10 navigation expert who worked for Air New Zealand at the time, agrees. He thinks the accident would never have happened had a navigator been on board. While the pilots were following a line on the navigation computer that put them 43km to the west of where they thought they were, other flight procedures to double-check that information should have been followed.
Why, he asks, did the crew not check the plane's coordinates, showing their position, with the chart on board which would have shown up the error that they were flying straight towards Mt Erebus.
Amies is clear about Civil Aviation regulations for Flight 901 that the plane should have been flying at 4876m with clearance to go down to 1828m after it passed McMurdo, where the highest point was 914m.
"For the life of me I don't understand it. He [Jim Collins] wasn't a captain who would take risks."
Amies speculates that the flight crew did not want to disappoint the passengers. "They had paid to see Antarctica and all they were going to see was cloud. There was no chance of doing it tomorrow." (Each Thursday in November, the flights were fully booked.)
The first sign that the crew knew something was wrong came 26 seconds before impact. Engineer Gordon Brookes, a friend of McGreal's, is heard on the black box recorder saying: "I don't like the look of this."
Captain Collins asks for full power as alarms start to sound but less than half a minute later, at 12.49pm, the 257 passengers and crew were dead, their bodies strewn across the snow with mangled, burned wreckage after the plane hit at 480 km/h.
McGreal remembers leaving the Civil Aviation office in Wellington that November evening feeling uneasy. News had raced through the office in the afternoon that an Air New Zealand DC-10, loaded with passengers on a sightseeing flight to Antarctica, had made no contact.
When Ron "Chip" Chippindale, Chief Inspector of Air Accidents, rang McGreal at home around 9 that night, he knew he was facing a major tragedy. Wreckage had been spotted on the lower slopes of Mt Erebus on Ross Island and there appeared to be no survivors. The two men went back into the office where McGreal made a list of files to be "frozen" ready for the inevitable inquiry.
First up was Chippindale's report, in 1980, which acknowledged the navigational error programmed into the Air New Zealand computer and later corrected, without the knowledge of the pilots.
That error led them to believe they were on a course which was in fact 43km to the west. Rather than coming down over the Ross Sea, they were flying straight into Mt Erebus.
Essentially Chippindale concluded that the pilot was flying below minimum safe altitude with no forward visibility.
Faced with public dissatisfaction with Chippindale's report, the then Prime Minister Sir Robert Muldoon appointed Justice Peter Mahon to head a Royal Commission of Inquiry. The findings of that inquiry, in 1981 - which accused Air New Zealand of a conspiracy and a cover-up - have caused the Erebus wound to fester for nearly 30 years. Mahon's famous quote, that he had listened to "an orchestrated litany of lies" from the airline, was to dog Air New Zealand for decades. Parts of Mahon's report were later condemned by the Court of Appeal and the Privy Council.
McGreal and Amies think Mahon was wrong. So does retired airline captain Ian Gemmell who this month described Mahon as "an idiot".
Amies, now 87, was accused by Mahon of lying and being part of the conspiracy. "I know in my conscience and in my mind that everything I told the commission was true."
Amies thinks that grieving family members are "more in the dark now than ever" because of the controversy and confusion which has dogged the accident.
Both Amies and McGreal are scathing of Mahon's handling of the inquiry, saying he took advice from people with "opinions" rather than sticking to sound aviation knowledge.
Amies believes Mahon did not understand how sacrosanct Civil Aviation guidelines for safe altitude are in the aviation industry. McGreal: "I think he died knowing he had made a mistake."
But Mahon's widow, Margarita Mahon, dismisses that suggestion. Instead, she says, her husband died (in 1986) disillusioned by his treatment by two Court of Appeal judges who handed out "scathing" criticism of his ability.
It was that criticism that forced Mahon to stand down from the bench, effectively ending his legal career. The family were left to live on a small pension before ill health overtook her husband, she said.
"I saw the pressure he was under. He was penalised. It was a very, very hard time."
In recent years she had felt "very, very sad" over the toll the aftermath of the inquiry took.
"It should never have happened the way it did. There should be some people out there feeling very guilty. I see it as a great blot to the New Zealand legal system."
Margarita Mahon said her husband never faltered over his conviction that he had done the job to the best of his ability and that he would have not changed his findings given the chance.
Earlier this year, on her 81st birthday, she stood on the stage at the SkyCity Convention Centre to a standing ovation from members of the international pilot community.
She had accepted a posthumous award for her husband, the Jim Collins Memorial Award for making an exceptional contribution to airline safety. "It was extraordinary. I couldn't find my voice."