Other major events On 18 September 1961, a DC-6 passenger aircraft of Transair Sweden operating for the United Nations crashed near Ndola, Northern Rhodesia (present-day Zambia).

[10] A special report issued by the United Nations stated that a bright flash in the sky was seen at approximately 01:00[10] that resulted in the initiation of search-and-rescue operations.

The Rhodesian Commission of Inquiry, under the chairmanship of Sir John Clayden, held hearings from 16 to 29 January 1962 without United Nations oversight.

The subsequent United Nations Commission of Investigation held a series of hearings in 1962 and depended partly upon the testimony from the previous Rhodesian inquiries.

The Rhodesian Board of Investigation sent 180 men to search a six-square-kilometer area of the last sector of the aircraft's flight path, but no evidence of a bomb, surface-to-air missile or hijacking was found.

The panel was led by Mohamed Chande Othman (the Chief Justice of Tanzania) and also included Kerryn Macaulay (Australia's representative to ICAO) and Henrik Larsen (a ballistics expert from the Danish National Police).

[18] Despite the multiple official inquiries that failed to find evidence of assassination or other forms of foul play, several people have continued to advance theories involving hostile interests.

The Belgian government had a vested interest in maintaining its control over much of the country's copper industry during the Congolese transition from colonial rule to independence.

[11][6] Major C. F. Westell, a ballistics authority, said, "I can certainly describe as sheer nonsense the statement that cartridges of machine guns or pistols detonated in a fire can penetrate a human body.

"[20] He based his statement on a large-scale experiment that had been conducted to determine whether military fire brigades would be in danger working near munitions depots.

Other experts conducted and filmed tests showing that bullets heated to the point of explosion did not achieve sufficient velocity to penetrate the containers in which they were stored.

However, Tutu's commission were unable to investigate the truth of the letters or the allegations that South African or Western intelligence agencies played a role in the crash.

Egge believed that Hammarskjöld had been thrown from the plane and that grass and leaves in his hands might indicate that he had survived the crash and tried to scramble away from the wreckage.

[24] In a speech to the UN General Assembly on 23 September 2009, Muammar Gaddafi demanded that Libyan UNGA president Ali Treki launch an investigation into crash as well as the death of Congolese prime minister Patrice Lumumba, who was overthrown in 1960 and murdered the following year.

Björkdahl reviewed previously unavailable archive documents and internal UN communications and believed that the plane was intentionally downed for the benefit of mining companies such as Union Minière.

It led to the formation of an independent, unofficial commission headed by the British jurist Stephen Sedley in 2012 to determine whether there was new evidence that would justify the UN reopening its 1962 inquiry.

A press release issued by the prime minister of the Republic of the Congo stated that "... in order to pay a tribute to this great man, now vanished from the scene, and to his colleagues, all of whom have fallen victim to the shameless intrigues of the great financial Powers of the West... the Government has decided to proclaim Tuesday, 19 September 1961, a day of national mourning.