For a long time, the 1961 plane crash that killed UN Secretary-General Dag Hammarskjöld has been a mystery: a nighttime catastrophe in Cold War Africa, unexplained and unexplainable.
In recent years, United Nations investigators have pushed for answers: What really happened to Hammarskjöld, a Swedish diplomatic titan who led the United Nations through Cold War rivalries and decolonization? Was it a tragedy? Or an assassination?
“We deserve answers,” Caroline Hammarskjöld, the diplomat’s great-niece, said in an interview. “If it was an attack, then we have the right to know.”
A much-anticipated report released by the United Nations this week said it provided no definitive answers because the lead investigator was “almost certain” that the United States, Britain, and South Africa had not disclosed all their documents related to the case.
The State Department said in a statement to The New York Times that the US had “cooperated extensively with this investigation, including by sharing thousands of pages of declassified documents.”
The British government declined to comment, and the South African government did not immediately respond.
The UN has vowed to keep pushing. In a preface to the report, António Guterres, the current secretary-general, said, “We owe this to the life and legacy of Dag Hammarskjöld and to the members of the party accompanying him.”
Late on Sept. 17, 1961, Hammarskjöld was traveling across southern Africa to broker an end to separatist fighting in Katanga, a mineral-rich province in the newly independent Congo.
It was a pivotal period for the continent as countries teetered between colonial rule and independence. Hammarskjöld, then 56, was a fierce advocate of Africa’s liberation (and would become the only person to be awarded the Nobel Peace Prize posthumously).
He knew his mission was dangerous. The United States was covertly supporting different factions within Congo, and Patrice Lumumba, one of Congo’s most charismatic political figures, had been killed by Congolese forces aligned with Belgium and the United States earlier that year.
As Hammarskjöld’s plane skirted Congolese territory, it observed near-total radio silence. Moments before it was set to land in Ndola, a city in today’s Zambia, it crashed.
The colonial authorities initially blamed pilot error. But newer evidence suggests foul play.
Mohamed Chande Othman, a former chief justice of Tanzania, has led the UN investigation into the crash for over a decade.
Othman, who declined to comment on the report released this week, wrote that both the United States and Britain knew of Hammarskjöld’s itinerary, as did people in the area, suggesting that an attack could have been planned.
Many witnesses saw two planes that night. According to the report, they said the other plane might have fired at Hammarskjöld’s. Several people recalled “a flash or light in the sky, or fire before impact.”
Othman noted that although 15 people on board died instantly, one passenger survived for a few more days, telling doctors that there had been an explosion aboard, followed by smaller explosions that forced the plane down.
The report refers to testimony from Charles Southall, a former American naval officer, who was monitoring radio traffic in Africa at the time. He has said he heard a radio transmission from a Belgian mercenary pilot the night Hammarskjöld’s plane went down.
“You could hear the gun cannon firing rat-tat-tat,” Southall told documentary filmmakers, “and he said, ‘I’ve hit it. There are flames coming out of it.’”
The UN report suggests that the United States, Britain, and South Africa hid the truth and are still doing so a lifetime later.
Colonial officials appear to have steered the investigation away from foul play, and suppressed the testimony of the surviving passenger at the time.
Susan Williams, whose 2011 book “Who Killed Hammarskjöld?” kick-started the UN reports, said the case had “the appearance of a cover-up.”
This week’s 83-page document was the sixth UN report on the crash since it reopened the investigation in 2014. Othman said his repeated requests for more information from the United States and Britain had been denied, while a South African process had sputtered and died.
“The lack of full disclosure remains the primary obstacle,” he said.
‘That Final Piece’
Even if the answers are hidden inside the stubbornly sealed archives of some of Sweden’s closest allies, investigators say the inquest must continue. The point is to send a message, said Jan Eliasson, a former UN deputy secretary-general: “The truth must take priority.”
Hans Kristian Simensen, a leading independent researcher, wants the Swedish government to open its own truth commission. He suspects foul play.
“It could also be pilot error,” he said. “But maybe a relevant question, then, is: Why are they still keeping classified documents if it was an ordinary air crash?”
Among those killed in the crash was Stig Olof Hjelte, a Swedish soldier, at age 21.
His brother Ingemar Hjelte has taken up the quest. The question for Hjelte, now 81, is not whether there was foul play. He’s certain of that. Instead, he wants “to know who gave the orders.”
“We still haven’t found that final piece of the puzzle,” he said: “the truth.”
This article originally appeared in The New York Times.