New Zealand Prime Minister Jacinda Ardern apologised on Thursday for the then-government’s handling of a plane crash in Antarctica 40 years ago that took the lives of 257 people in the country’s worst peacetime disaster.

On 28 November 1979, Air New Zealand flight 901 was on a sightseeing tour from Auckland when it crashed into the side of Mount Erebus, a 3 794 metre volcano near the US Antarctic research base of McMurdo Station.

Most of the 237 passengers and 20 crew killed were New Zealanders but other nationalities included Americans, Canadians, Japanese and Australians.

Originally the crash was blamed on the pilots, but following a public outcry, a Royal Commission of Inquiry was set up to investigate the disaster.

It concluded the main cause of the accident was the state-owned airline’s actions in reprogramming the aircraft’s navigation system without advising the aircrew.

The Commission head, former justice Peter Mahon,controversially also said witnesses from Air New Zealand had conspired to give false evidence, famously describing the airline’s defence as “an orchestrated litany of lies”.

This led to his report being criticised by both Air New Zealand and the government.

The actions of the then government and the airline caused more pain and grief to the victims’ families, Prime Minister Ardern said at a memorial service at the Government House in Auckland on Thursday.

“After forty years, on behalf of today’s government, the time has come to apologise for the actions of an airline then in full state ownership; which ultimately caused the loss of the aircraft and the loss of those you loved,” Ardern said in her speech.

“The pilots were not responsible for this tragedy, and I stand here today to state that again,” she added.

Ardern acknowledged the findings of the Royal Commission were not accepted by the government of the day, and it was only nearly 20 years later the report was even presented in parliament.

In 2009, Air New Zealand apologised to the families of the victims for mistakes made by the airline in the aftermath of the crash, and on Thursday Air New Zealand Chairperson Therese Walsh also expressed regret.

“I apologise on behalf of an airline which 40 years ago failed in its duty of care to its passengers and staff,” said Walsh.