Image copyright Getty Images Image caption TE901 crashed head-on into the gentle slopes of Mount Erebus

It remains New Zealand's worst peacetime disaster. On 28 November 1979, a sightseeing aircraft carrying 257 people crashed head-on into the side of a volcano in Antarctica.

The tragedy of flight TE901 was a shock for New Zealand, affecting almost everyone in the country in some way, and led to years of investigations and a bitter blame game.

And the legacy of the Mt Erebus disaster is still felt 40 years on.

How did the plane crash?

Air New Zealand had started operating scenic flights over Antarctica only two years before, and they had been a great success.

What better way to spend a day than to cruise on an 11-hour non-stop round trip from Auckland down the length of the country and on to the great southern continent? The flights offered first class luxury and a stunning view over the endless ice at the edge of the world.

But on that day in 1979, things would go very wrong.

At around noon, the pilot Capt Jim Collins flew two large loops through the clouds to bring the plane down to about 2,000ft (610m) and offer his passengers a better view. Assuming he was on the same flight path as previous flights and over the vast McMurdo Sound, he wouldn't have foreseen any problems.

On board the DC 10, people were busy taking photographs or filming in the cabin and out of the windows. Many of these photos were later found in the wreckage and could still be developed, some of them taken seconds before the crash.

But instead of ice and snow in the distance, what the cockpit was looking at was the mountain right ahead of them. Shortly before 1pm, the plane's proximity alarms went off. With no time to pull up, six seconds later the plane ploughed straight into the side of Mt Erebus.

After hours of waiting and confusion, the assumption back in New Zealand was that the plane must have run out of fuel. Wherever it was, it was no longer in the air.

Search and rescue operations were dispatched and soon confirmed the worst fears: wreckage was spotted on Ross Island, on the lower slopes of Mt Erebus and it was clear there'd been no survivors.

"That same accident would not happen on a modern airliner," Captain Andrew Ridling, head of the New Zealand Air Line Pilots Association, told the BBC. In part, that's because of lessons learned from crashes like the one of TE901.

"The equipment today is extremely good. You've got a satellite based navigation system, so being on the wrong flight path like that would just not be possible."

Shattering national identity

Two main reasons have been determined as the cause of the crash.

The pilots had been briefed with a flight path which was different from the one put into the plane's computer. The team thought their route was the same as previous flights, going over ice and water in the McMurdo Sound, when in fact the path was going over Ross Island - and the 3,794m volcano Mt Erebus.

The second cause was a weather phenomenon known as whiteout - and that's what is likely to have sealed the plane's fate.

The whiteout meant the light between the white snow or ice underneath and the clouds overhead created an illusion of clear visibility. The pilot trusted the automatic flight path, assuming the white he was seeing through the cockpit window was simply the ice and snow on the water below, not the face of a mountain.

The crash killed 227 passengers and 30 crew. Forty-four people were never identified during the search and recovery operations.

New Zealand's population was then only around three million people. As people said at the time, almost everyone was somehow connected to the Erebus disaster, whether through knowing a victim, a member of the many heroic recovery operations, or taking sides in the lengthy legal battle that ensued.

And the tragedy left New Zealand in shock.

"It came at a time the relatively young nation was in a crucial period of finding a new narrative for its identity," explains Rowan Light, a historian with Canterbury University.

"In the 1960s and 70s the old narrative of being a progressive outpost of the British Empire had fallen to pieces or was just not making sense any more," he says.

But the country was trying to find its feet. Technological advances were a big part of that new path, infrastructure was key to the national story of settling, conquering and gaining control over the land. And reaching out to Antarctica, about 4,500km (2,780 miles) to the south, fitted perfectly into that story.

Yet a row of terrible disasters was to profoundly shake that sense of self.

Image copyright Colin Monteath/Antarctica New Zealand Image caption Air New Zealand had been an object of pride and prestige

A train crash at Tangiwai in 1953 had left 151 people dead and the Wahine ferry disaster in 1968 had killed 51 people. The Mt Erebus crash was the third in that list and by far the deadliest.

"So you had this really interesting moment with those disasters because they really called into question that narrative of technological progress and control," Mr Light explains.

That legal battle came swiftly and was a second blow after the crash itself. New Zealanders were shocked by the failure to properly identify what had happened and by the bitter accusations.

Image copyright Phil Reid/Antarctica New Zealand Image caption Wreckage from the plane is still at the mountain

The first investigation essentially found the pilots at fault.

They had flown well below the minimum safe altitude set by the airline and it seemed easy to say that sticking to that minimum would have prevented the crash.

While the investigation had also uncovered the mismatch in the flight paths, it nonetheless concluded that a higher altitude would have saved the plane from crashing.

'An orchestrated litany of lies'

Putting the blame on the pilots proved controversial, though, and a second investigation was launched, this time a Royal Commission of Inquiry, New Zealand's highest level of public inquest. The results couldn't have been more different: this time, the blame landed squarely on Air New Zealand.

Yes, the plane had been well below the safe altitude - but the inquiry found that the Antarctic flights had routinely flown at such extremely low levels to provide a better view for its paying customers.

Even a promotional brochure for the scenic route had boasted of the scenery using photographs clearly taken from a way below the safe altitude.

The Royal Commission did not only find that the airline was to blame due to the mistakes in the flight path, but it also alleged that Air New Zealand had essentially tried to cover up its own responsibility: a conspiracy to blame the pilots leaving Air New Zealand morally in the clear - and also in terms of compensation payouts to the victims' relatives.

Famously, the head of the inquiry, judge Peter Mahon, described the airline's defence as "an orchestrated litany of lies" - a phrase which would stick in the national consciousness.

'A sense of betrayal'

The airline took the case to an appeals court and won, with Mr Mahon's allegation they intentionally had obscured the crash causes overturned.

Again, the Erebus tragedy was in limbo, and the blame game grotesquely overshadowed the relatives' grief.

Image copyright Getty Images Image caption There have been several memorials at the crash site - like this one in 2011

The TE901 crash was also a serious blow to Air New Zealand's reputation.

The airline had very much been a source of pride for the country - as national carriers are, it was part of the fabric of how New Zealand saw itself on the global stage. But over the years, the overwhelming consensus became that the airline had indeed been at fault and not the pilot team.

It never ran the Antarctic flights again - though one private airline does cover the sightseeing route from Australia.

At the time, the crash and its aftermath were seen as "almost a sense of betrayal for people", Mr Light explains.

In 2009, Air New Zealand issued a first apology - although only for its behaviour in the aftermath, not for the actual accident itself.

But on this year's anniversary, the airline finally issued that full apology that so many people felt was overdue.

"I apologise on behalf of an airline which 40 years ago failed in its duty of care to its passengers and staff," the airline's chairwoman Therese Walsh said at the commemorations at government house in Auckland.

"While words will never bring back those lost on Mt Erebus this day 40 years ago, I would like to express regret on behalf of Air New Zealand for the accident which took the lives of 257 passengers and crew."

Prime Minister Jacinda Ardern also used the day to give a first full apology by a New Zealand government.

"This apology is whole hearted and wide reaching," she said. "We will never know your grief, but I know the time has come to say I am sorry."

New Zealand's loss of innocence?

Forty years on, the crash remains a story crucial to New Zealand's recent history.

For the post-war generation, it was the biggest tragedy they'd witnessed their country go through and there's a lingering sense that it might have been where the young nation lost its innocence, its clear sense of direction, stability and trust in the established order.

Despite this, there is as yet no national memorial to the victims.

A cross and a koru - a stone coiled fern - have been placed near the crash site and Ross Island has been witness to several commemoration events by the victims' relatives, but the debate of what form a memorial should take and where it would go has generated its own frustrations.

Earlier this year, New Zealand approved a plan for a structure in Auckland, which Prime Minister Jacinda Ardern said "reflects the enormity of the tragedy and provides a strong sense of connection and loss".

As the country remembers the crash this Thursday, thousands of miles away, the ruins of the aircraft still lie on the slopes of Mt Erebus.

Partially covered by snow, the wreckage is a silent tribute to the flight of a lifetime that ended in tragedy.