At about twenty to two on the morning of 28 November 1979, someone in Air New Zealand’s navigation section changed two numbers in a computer.

The McMurdo waypoint stored in the ground system moved roughly two degrees and fifteen minutes of longitude to the east. It was a correction, made in good faith, to bring the stored coordinates into line with a beacon.

Nobody told the crew. Eleven hours later, 257 people were dead on the side of a volcano.

A route that was never quite the route

Air New Zealand had been running Antarctic sightseeing flights since 1977. They left Auckland in the morning, spent several hours over the ice, and came home the same day. There was a commentator on board. On this flight it was Peter Mulgrew, standing in for Sir Edmund Hillary, who had cancelled.

The route approved by the Civil Aviation Division ran from Cape Hallett to the McMurdo non-directional beacon. As it happened, that track passed almost directly over the summit of Mount Erebus, which was fine, because it was flown at altitude.

Then the route was computerised, and a typing error crept into the coordinates. The flight plan the airline actually issued sent aircraft down the middle of McMurdo Sound instead, some 27 nautical miles west of the mountain. Thirteen previous flights had flown that way, none of them aware that what they were flying was not what had been approved.

On 14 November, Captain Leslie Simpson flew one of the trips and noticed that the McMurdo waypoint in his aircraft’s inertial navigation system sat a surprising distance from the McMurdo TACAN beacon. He reported it.

That report set off the correction made in the small hours of the 28th. The waypoint was moved to match the TACAN. The new track no longer ran down the sound. It ran into the mountain.

Two aeroplanes, one crew

Captain Jim Collins, 45, had 11,151 flying hours. First Officer Greg Cassin, 37, had 7,934. Neither had been to Antarctica before. Collins had spent the previous evening at home marking up his own charts from the briefing he had attended on 9 November.

Those charts showed the McMurdo Sound track. The computer in the aircraft, loaded that morning, had the new one. From the moment the coordinates went in, the crew were flying one route and navigating by another.

Below a cloud base later estimated at 600 to 900 metres, Collins flew a figure-eight to descend through a gap and get the passengers a view. He told McMurdo he would come down to 600 metres and engaged the autopilot. American controllers had offered a radar letdown to 460 metres, but their radar never picked the aircraft up, VHF communications were difficult, and the DME would not lock onto the TACAN for any useful period.

So the aircraft flew on, straight and level, under an autopilot following a route the crew did not know they were on, towards a mountain they could not see.

Why they could not see it

This is the part that is hardest for people to accept, and it is the part passenger photographs settle. Pictures taken seconds before impact show clear visibility beneath the cloud base, with landmarks visible 21 kilometres to the left and 16 kilometres to the right. They were not flying in cloud.

What they were in was a sector whiteout. A layer of cloud above blended seamlessly with the snow-covered slope ahead, erasing the contrast between ground and sky and producing the illusion of a flat, distant horizon. The crew believed they were looking across open water at the Ross Ice Shelf. The shelf was behind the mountain.

Mahon later called it a malevolent trick of the polar light. Air New Zealand had given its crews no training on the phenomenon at all.

A concise account of the flight and what the crew were seeing in the last minutes.

Six seconds

At 12:49 the ground proximity warning system began sounding. The flight engineer called five hundred feet, then four hundred. Collins called for go-around power.

Six seconds later the aircraft struck the lower slopes of Mount Erebus at about 460 metres and exploded. Everyone on board was killed instantly.

Debris was spotted from the air at five to one the following morning. Search parties landed on the mountain around nine, twenty hours after impact. The recovery, named Operation Overdue, ran until 9 December with up to sixty people working on the slope at a time. Eventually 83 percent of those on board were identified. Forty-four were not individually identified.

Two inquiries, two answers

Chief Inspector of Air Accidents Ron Chippindale reported in June 1980 and found the principal cause to be pilot error: Collins’s decision to descend below the customary minimum and to continue at that altitude when the crew were unsure of their position.

Public dissatisfaction produced a one-man Royal Commission under Justice Peter Mahon, who reported in April 1981 and cleared the crew.

Mahon went further. He found that airline executives and senior pilots had covered up evidence and lied to investigators, and delivered the phrase that entered New Zealand’s language for a generation: an orchestrated litany of lies.

What survived the appeals, and what did not

This distinction matters, and it is routinely blurred.

Air New Zealand challenged Mahon’s costs order and some of his findings. The Court of Appeal unanimously set aside the costs order but, by majority, declined to disturb the conspiracy finding. Mahon then appealed to the Privy Council, which delivered judgment in October 1983 under Lord Diplock.

The Privy Council accepted that evidence given by several executive pilots had been false, but held it could not have formed part of a predetermined plan of deception. It found Mahon had breached natural justice in finding a conspiracy the evidence did not support, and dismissed his appeal.

Crucially, his finding on cause was never challenged, and therefore stands. The crash was the result of the aircrew being misdirected as to their flight path. It was not pilot error. What the Privy Council struck down was the accusation of an organised cover-up, not the explanation of why the aeroplane hit the mountain.

New Zealand television’s contemporary documentary treatment of the disaster and the inquiries that followed.

A detailed breakdown of the navigation error and the two competing investigations.

Forty years to an apology

Mahon’s report was not tabled in the New Zealand Parliament until 1999, eighteen years after he wrote it. In 2008 he was posthumously given the Jim Collins Memorial Award by the country’s airline pilots, named for the captain he had exonerated.

Air New Zealand’s chief executive apologised in 2009 to those who had not received proper support. On the fortieth anniversary in November 2019, Prime Minister Jacinda Ardern apologised on behalf of an airline that had failed in its duty of care to its passengers and staff.

Almost all of the wreckage is still on the mountain, buried under snow in cold seasons and visible from the air in warm ones. An aluminium cross stands above Scott Base, replacing a wooden one that the Antarctic weather destroyed. The registration ZK-NZP has never been used again.

The last Air New Zealand DC-10 flew in December 1982. Antarctic sightseeing charters from New Zealand did not resume until 2013.

Sources: Report of the Royal Commission to Inquire into the Crash on Mount Erebus (Mahon, 1981); Aircraft Accident Report 79-139 (Chippindale, 1980); Judicial Committee of the Privy Council judgment, 20 October 1983; New Zealand Court of Appeal; Inspector Jim Morgan’s report on the recovery operation; Archives New Zealand.