On Nov. 28, 1979, Air New Zealand Flight 901 was on a sightseeing tour of Antarctica. The 11-hour first-class tour from Auckland included a champagne breakfast and premier views of the frozen beauty of Antarctica. Most of the passengers were New Zealanders, but there were also Australians, Americans, Canadians and Japanese on board.

Shortly before 1 p.m., the plane crashed into the side of Mount Erebus, a volcano, killing all 257 people on board. It was New Zealand's worst peacetime disaster.

On Thursday, exactly 40 years after the crash, New Zealand's prime minister, Jacinda Ardern, apologized to the families of those killed for the then-government's handling of the tragedy. It was the first full apology for the crash by a New Zealand government.

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

Ardern, speaking at a memorial in Auckland, told family members of the victims that their loss was huge. "But that loss and grief was compounded. It was undeniably worsened by the events that followed".

There were several inquiries after the crash to determine what caused the state-owned aircraft to slam into the side of Mount Erebus. An initial investigation blamed pilot error, but many in New Zealand accused the government of trying to cover up for the national airline.

The public outcry led to a second investigation in 1980 by a Royal Commission. It found the cause of the disaster was because the aircraft's flight path had been changed without telling the pilots.

The head of the commission, Justice Peter Mahon, described Air New Zealand's participation in the investigation as "an orchestrated litany of lies."

Mahon's findings were not accepted by the airline or New Zealand's government at the time.

Speaking on Thursday, Ardern said the commission's findings were "never received by the government of the day in the way it should have been." She added that the "findings have always stood," and described Thursday's apology as "recognition of the findings of that report, all those many, many years ago."

Ten years ago, Air New Zealand issued its first apology, but only for its actions after the crash, not for the crash itself. Speaking at Thursday's memorial, Dame Therese Walsh, the current chairperson of Air New Zealand, issued a full apology to the families, saying "better care should have been taken of you" in the aftermath of the accident.