What Caused the 1961 Crash that Killed UN Secretary General Dag Hammarskjöld?

In 1961, a plane carrying Dag Hammarskjöld, the UN Secretary General, crashes in what was then known as northern Rhodesia in Africa. What followed was a series of investigations and conspiracy theories that left the public asking for generations what really brought down the plane that carried one of the most important men in the world? Was this just an accident – or a sinister plot to assassinate a diplomat advocating for peace? In Episode 51 of Take to the Sky: the Air Disaster Podcast, we explore a story full of secrets, lies, and mysteries that have endured for over 50 years. 

The 1961 United Nations Flight into Ndola

On the late night of September 17, 1961, The Albertina, a Douglas DC-6 transport aircraft, departs from Leopoldville, which is the capitol of The Congo, now renamed Kinshasa. But this is no ordinary flight. The Albertina is on a secret, six-hour flight toward the airport in Ndola, Rhodesia, a region in Africa that we refer to today as Zambia. 

One of the most famous men in the world at the time is a passenger on this flight. He is Dag Hammarskjöld, and he is the youngest and second-ever Secretary General of the United Nations (or UN). BTW, he remains the youngest ever Secretary General to this day. Ten others join Hammarskjöld in his entourage, including members of his UN staff and security guards. 

A Swedish flight crew is piloting The Albertina and includes Captain Per Hallonquist, First Officer Lars Litton, and flight engineer Nils Goran Wilhelmsson. In all, there are just 16 people onboard. 

At the time of this important flight, Hammarskjöld is in his second term as Secretary General and is flying to Ndola to conduct secret peace talks in The Congo. 

Who was Dag Hammarskjöld?

On November 10, 1952, 9 years before this flight, the first-ever Secretary General announced his resignation. The superpowers (including the US and the Soviet Union) hoped to seat a Secretary-General who would serve a more administrative role and less of an active political role, which of course, could interfere with a country’s agenda. Hammarskjöld's reputation at the time was, in the words of biographer Emery Kelèn, "that of a brilliant economist, an unobtrusive technician, and an aristro-bureaucrat". As a result, he was selected to be the second Secretary General with very little controversy. Everyone thought he was going to be a boring bureaucrat. They were wrong. 

Immediately following his seating, Hammarskjöld attempted to establish a good rapport with his staff at the UN. He visited teams in every single UN department to shake hands with as many workers as possible, he chose to eat in the cafeteria as often as possible to be visible to and among his staff, and he converted the private elevator that was intended only for the Secretary General to be available for use by anyone. 

Why was Dag Hammarskjöld flying to The Congo in 1961?

The world in late 1950s and early 1960s was not a very stable time in history. The events surrounding the crash featured in this episode take place during the Cold War, and during the era of decolonization in Africa, and these events matter a lot to this story. 

As the Cold War raged on between the Superpowers, the Congo had won its independence from Belgium. However, its southern region, known as Katanga, then declared itself independent of The Congo. Consequently, a bloody civil war broke out. This situation was considered a high priority to the Superpowers because Katanga had the world’s largest uranium reserves. And as we know, uranium was used to make both the atomic bombs that the US detonated over Japan, which meant, whomever had control over these reserves would have access to powerful resources that could shift the tide of The Cold War. This also means that different Superpowers are also backing opposing forces. And ultimately it means the risk of a nuclear war is real. This is why Hammarskjöld is traveling on this high-stakes mission with the goal of peacefully reuniting the Congo by conducting secret peace talks with the leader of the counter forces, the Katangese Prime Minister, Moise Tshombe.

Hammarskjöld’s Secret Flight into Ndola

With all this political turmoil unfolding in The Congo, this top-secret flight is a security risk to Hammarskjöld and his staff. In fact, mercenary pilots are often hired to shoot down transport planes just like this one – this plane is basically flying into a combat zone. And if these circumstances are not enough, the airport in Ndola is also a very difficult one to fly into. It is surrounded by hilly terrain and lots of dense vegetation and scattered forest. And, to top things off, they are flying into the airport at night. 

Acutely aware of these risky circumstances, the pilots have taken every precaution to keep the destination and nature of the flight a secret: to prevent an ambush, they have NOT filed a flight plan; to make the plane less of a target while in the air, they choose an indirect route to get them into Ndola; and to avoid transmitting information about who is onboard and where they are headed, pilots maintain radio silence. When Ndola controllers ask the flight crew to declare their intent and final destination after Ndola, the crew tells the controllers, “We will let you know once we are on the ground.” This is how secretive this mission – and this flight – are. 

It is nearly midnight, and now the Albertina is getting closer to the airport. The pilots take the plane into a descent toward 6,000 feet and begin to perform their customary landing checklists in preparation for their arrival. At this point, the plane is about 10 minutes away from the airport’s only runway, and the pilots confirm with air control that they can see the runway lights shining through the night sky in front of them. As we mentioned, Ndola airport is difficult to fly into. For the final approach, the crew performs a final turn – this is because they must actually fly past the airport and perform a wide swooping, left-hand turn to line them back up with the only runway. 

But just minutes later, a little after midnight, controllers at Ndola airport are growing concerned. The Albertina is now overdue. Worried, controllers call other regional airports, thinking perhaps The Albertina has, at the last moment, changed its course. But they discover the plane has not landed elsewhere. By dawn, rumors begin to erupt among the awaiting journalists in Ndola who have been authorized to cover the UN peace talks. 

About four hours later, several journalists are so concerned about the welfare of the Secretary General and his staff that they charter their own plane to initiate a search for the missing aircraft. In the afternoon sunlight across the Rhodesian terrain, they make a horrifying discovery just a little over 9 miles (or 15 kilometers) west of the airport.

On the ground below, is a large gash across the landscape, and inside it is the smoldering wreckage of a plane. It is the Albertina. All around the wreckage, the forest trees have been sliced down to their stumps. From the appearance of the crash site, it is clear that the plane has come down hard through the trees, and with great force, impacting the ground and exploding into a large, engulfing fireball. 

Soon after being notified of the crash, the Rhodesian police secure and block off the crash site – not even the journalists who found it are permitted close to it. The police immediately see bodies interlaced between blocks of burnt wreckage. The fire was so extreme, that 80% of the wreckage is melted. Many of the passengers’ personal effects are also found in the wreckage along with important pieces of evidence: their wrist watches, which all stopped at exactly the same time – 12:03 am on September 18th – the time of the impact and just 3 minutes after the crew’s last transmission to control. 

Amazingly, one survivor is found, though very badly burned with severe injuries, and is taken to hospital immediately. He is Sergeant Harold Julien, a UN Security officer. Everyone else onboard, including Dag Hammarskjöld and members of his UN congregation, are dead. 

Hammarskjöld’s death shocks the world, and immediately, rumors abound that the plane was brought down intentionally and that he was assassinated. Pictures of his memorial services back in Uppsala, Sweden, are seen all around the world, and a poignant moment comes when his family lays a wreath at his gravestone, and it has one word on it: WHY?

But while many mourn his loss, it is important to also recognize that not all governments were sorry Hammarskjöld was gone – in fact, it is clear how tenuous this moment is when no one else immediately comes forward to take up this particular mission to continue with the planned peace talks in The Congo. 

The 1961 Investigation into the Crash that Killed Dag Hammarskjöld

Back on the ground in Rhodesia, the Rhodesian Board of Investigation begins to explore the cause of the crash. The investigation will be a difficult one, because of the melted airplane and because the DC-6 has no flight data or cockpit voice recorders. And this will be the first in a series of three investigations into the crash over the next few years. 

One of their first actions is to get the account of the lone survivor, Sergeant Harold Julien – and what he tells investigators is absolutely shocking. He is heavily medicated and in an enormous amount of pain, but his few words point toward a disturbing possibility. He tells them that right before the crash, Hammarskjöld shouted out, “We have to go back!” And then Julien says, he saw sparks in the sky, and then the plane blew up. And then it crashed. 

Clearly investigators look forward to getting more information from him as he recovers, but their hopes of doing so are soon dashed. Sadly, Julien dies just 5 days after the crash, succumbing to his injuries. 

One of the most immediate questions for investigators to next answer is, was the plane blown up or shot down? Apparently, the rebel forces in Katanga had obtained a French Fouga fighter jet, but the location of the base where the jet would have had to have taken off from and where they would have to had shot at the plane in order not to be seen was too far a distance to make that possible. Basically, the jet would have needed more launching range than was possible in order for them to fire the missile and then get back to the base without running out of fuel. Investigators also find that neither the airplane’s skin or fuselage or even the soil at crash site show evidence of missile or bomb. There is no evidence on any of the wreckage, so, they rule out either the possibility of the plane being blown up or shot down.  

They also rule out maintenance issues, even though right before this flight, one of the Albertina’s engines had been hit by gunfire. Repairs had been done and the plane had been declared safe for duty. Investigators wondered, what if the engine failed and caused the plane to lose altitude? When they examine the damage to the fan blades on each engine, they confirm that, as the plane was crashing toward the ground, all engines were working properly, so this is also ruled out.

Investigators next study the navigational chart for the flight path and calculate the altitude that the plane SHOULD have been at when it was in each location along the route. Their calculations show that the plane should have been 1700 feet higher than it was when it first hit the trees. In fact, the wreckage demonstrates that the aircraft impacted the trees and then traveled forward for another 750+ feet before impacting with the ground. Investigators can tell the plane came in at a shallow angle, just like the angle one would expect to see from a plane that is preparing to land – as it certainly was. Their takeaway here is, the plane was coming in at too low an altitude. But, investigators confirm that the altimeters were correctly set, so they know that an incorrect altimeter reading did not lead the pilots to descend too low. So, what did? 

Investigators go back to the controller transmissions. Remember, there is neither a flight data recorder (FDR) nor a cockpit voice recorder (CVR) available, but the transmissions to control are available. And investigators hear Captain Hallonquist say, “descending” at a point in the flight path when it would have been too soon to do so. Everything begins to point to a plane that was ready to land – they were descending, the landing gear was down, and the flaps were extended. This crash, at least to investigators, is looking more and more like pilot error. 

They put these facts side by side with one other fact that to them paint the picture of pilot error: on the day of the crash, they found another person in the cockpit, a UN bodyguard. Investigators believe that this person likely came into the cockpit to get a status update on their arrival, but during a landing, a pilot’s workload is very high, and they need every last bit of their attention focused on only that. Investigators hypothesize that the presence of another person in the cockpit reduced the pilots’ altitude awareness. 

There is one last thing investigators must reach a conclusion about. Medical examination of bodies show that several bodies were riddled by bullets. 342 bullets in total. But because there was no evidence in the plane’s fuselage or crash site of a missile or bomb AND the bullets do not show evidence of having been fired from a gun, investigators deduce that the bullets must have belonged to the several security personnel traveling onboard and must have exploded upon impact, ripping into the bodies of those sitting closest to the security guards. 

The official conclusion by the Rhodesian Board of Investigation is pilot error. But the public does not believe it – it is a lot to ask people to believe, that the UN Secretary General simply died in a terrible but explainable accident. 

Subsequent Investigations from 1961 to 1963

Two more subsequent investigations, one conducted by the Rhodesian Commission of Inquiry and one conducted by the United Nations Commission of Investigation, support conclusions of the 1st one. However, the UN Commission was split between pilot error and an intentional takedown. There was not enough evidence, to them, that pointed with certainty to either one. Pilot error, for now, stands as the primary cause. 

The 2011 Journalistic Investigation into the Ndola United Nations Crash

However, to many in the public, the suspicion that the plane crash was an assassination never goes away. And to many, the truth of what happened to Dag Hammarskjöld has been covered up for decades. 

In 2011, in preparation for the 50-year anniversary of the crash, people had been on the ground in present day Zambia (previously Rhodesia) re-interviewing witnesses and conducting their own investigation into the crash. They wonder if, because of the passage of time, there would be different conclusions as to what really happened? Or had the truth already been surfaced, just not accepted by a shocked and heartbroken public prone to conspiracy theories?

Journalists Investigate the Crash that Killed Dag Hammarskjöld

Journalists from The Guardian and a Swedish aid worker living in Africa named Goran Bjorkdahl begin to investigate the 1961 crash. Here is some of the information uncovered by these 2011 investigations – and they are explosive findings. Firstly, African witnesses had either been disregarded back in 1961, or they were too afraid to come forward. Think of it like this, witnesses thought, if they could get to Dag Hammarskjöld, what would be done to me? But now, their stories are documented and corroborated. Many witnesses report seeing the DC6 being trailed by a smaller airplane that night. Some even say they saw the smaller plane fire at the larger plane, causing it to catch fire and crash into the hillside. Over and over journalists hear this same story repeated. 

Secondly, the investigative journalists also found previously unpublished telegrams and documents that plainly show tensions between the US and Britain and Hammarskjöld. Everyone thought he was going to be a boring, predictable bureaucrat. They were wrong, He was a blazing idealist. 

Political Tensions Heat Up Between the Superpowers and Hammarskjöld

By the time of his trip into The Congo in 1961, Hammarskjöld had deeply angered almost all the major superpowers at the time by supporting the decolonization of Africa. But, developing countries supported his position on decolonization, which meant that Hammarskjöld had the support he needed to be re-elected as Secretary General the following year.

Allegedly, the British and US were enraged at Hammarskjöld for an aborted UN military operation that he had ordered on behalf of the Congolese government against the Katangese rebels. On the surface, and publicly, the powers backed this operation. Privately, Hammarskjöld believed officials from both governments, and from Britain in particular, were obstructing peace moves, possibly as a result of mining interests and sympathies with white colonists on the Katanga side. This, of course, all points to motive. 

Here is what else the journalists found out:

• The officials who secured the crash scene, among them Rhodesian and British officials, took actions that delayed the search for the missing plane. In fact, the crash site was not recovered for 15 hours after the plane crashed.  Allegedly, there was a British official at the airport who misled controllers by telling them that the Albertina had changed course.
• Based on eyewitness accounts of residents in the area, the Albertina was most definitely shot down by a second plane. We explored this earlier.
• Sergeant Julien Harold could have survived; instead, he was intentionally let to die by not moving him out of the poorly equipped, local hospital. This is later corroborated in email by the very doctor who treated him. The doctor said clearly: “I look upon the episode as having been one of my most egregious professional failures in what has become a long career.” He admits to not trying hard enough to get Sergeant Harold moved, a change which would have likely enabled his survival.
• Related to the tensions between Hammarskjöld and the British, on the morning of September 13th, (the leader of the Katanga separatists) signaled he was ready for a truce, but then after a one-hour meeting with the UK consul in Katanga, he changed his mind. What was said in that meeting? Very suspicious

Susan Williams’ Investigation: A Mercenary Pilot Killed Dag Hammarskjöld

Later that year, also in 2011, University of London scholar and author, Susan Williams, published her book Who Killed Hammarskjöld? And its main premise challenges the conclusions that the crash was an accident. Instead, Williams points to the existence of US National Security Agency (NSA) radio intercepts of warplanes in the area during 1961, which are still top secret after 50 years. 

These transmissions identify that a Belgian mercenary pilot named Jan van Risseghem was flying a Katangese jet that night. Van Risseghem was never questioned during any of the official inquiries. In her book, Williams provides the account of an American naval pilot, Commander Charles Southall, who was working at the NSA listening station in Cyprus in 1961. Shortly after midnight on the night of the crash, Southall and other NSA officers heard an intercept of a pilot’s commentary. 

The pilot is heard saying: “I see transport plane coming low. All the lights are on. I’m going to make a run on it. Yes, it is the Transair DC6. It’s the plane.” They then hear the sound of gunfire and then the pilot is heard exclaiming, “I’ve hit it. There are flames! It’s going down. It’s crashing!” 

This evidence corroborates what the pilot himself allegedly told his friend. The friend, Pierre Coppens, only agreed to go on record with this account because van Risseghem was dead. 

By his own account as told to Coppens, Van Risseghem had rare skills in the cockpit. He claimed he could get “an iron with wings” into the sky, and said he was one of just a handful of pilots on the rebel air force who could fly in the dark. And in his daring escape from the Nazis, followed by years of service, he had shown he had the courage and the skills to go on a night-time attack that would take his plane to the limits of its range.

As reported in The Guardian, Coppens said Van Risseghem laid out the details of a complicated, logistically challenging plan. He used a Fouga jet – the last one remaining to rebel forces after one was seized by the UN and another destroyed in a crash.

He stripped out everything he could from the plane, making room to install a cannon for the attack, and reducing weight to increase his range, he told Coppens. He added extra fuel tanks and left from the airport at a town called Kipushi, far closer to Ndola than other airports, but not previously considered as a possible launch site for an attack because its short dirt runway posed a huge challenge for a jet to take off from. 

This all explains how a jet could have taken off, fired at The Albertina, and returned without encountering fuel issues. This account refutes what the original 1961 investigation had ruled out. 

The 2019 Documentary, Cold Case Hammarskjöld

A documentary about the plane crash came out in 2019 called Cold Case Hammarskjöld, which is by Mads Brugger. The documentary is intense and includes a claim that veers hard right off the road. Basically, it claims that a South African clandestine military organization for hire worked through back channels with the CIA and MI-6 to hire Van Risseghem to take down the plane. The most disturbing theory articulated in the documentary is that the only picture of Hammarskjöld’s body at the crash site shows him laying dead on a stretcher. And carefully tucked into his shirt collar is a playing card – the ace of spades. One of the members of the clandestine organization interviewed in the documentary explained the card: he said, in the 1960s, this card was left behind at a death scene to conveyed that this act was a hit carried out by the CIA. 

This plan to assassinate Hammarskjöld was laid out in secret documents by this clandestine organization discovered in the 1990s during the Truth and Reconciliation process in South Africa. Nothing was done with the documents at the time in terms of investigation (it was not a priority at the moment), but the same documents were later discovered by journalists and resurfaced in the 2010s. Basically, the allegation is that the British and American intelligentsia, probably along with South African intelligentsia, outsourced the assassination to this clandestine organization as a way to hide their participation. 

The Ongoing UN Inquiry into the Crash That Killed Dag Hammarskjöld

These journalistic discoveries led to the UN opening a commission looking into the allegations. There have been proceedings happening since 2013. 

The most recent report was published by the lead investigator appointed by the UN, former Tanzanian chief justice Mohamed Chande Othman in 2019. In the 95-page report, Othman said it “appears plausible” that the plane crash might have been caused by “an external attack or threat.”

Furthermore, Othman, complained that four countries – Britain, the United States, South Africa and Russia – have failed to provide any substantial response to his requests for information from their intelligence and security archives. This would include NSA and other intelligence agency records. As also reported in The Guardian, Othman said Britain, South Africa and the United States are almost certainly holding “important undisclosed information” about the plane crash, including intelligence reports and intercepted communications. This information could be the “missing link” in the mystery, he said. Because of the lack of a response from the four countries, he requested more time to complete his investigation.

In the investigative report, Othman recommended that an independent person is appointed to continue the work; that key member states (i.e., the US, the UK, and South Africa) again be urged to (re)appoint independent high-ranking officials to determine whether relevant information exists within their security, intelligence and defense archives; that a conclusion be reached over whether member states have complied with this process; and that key documents be made public.

In December 2019 a resolution was adopted to extend Othman’s mandate to investigate, with 128 countries signing on in agreement with the resolution. Once again, the resolution was not supported by either the US or the UK. As of 2021, the inquest is currently ongoing but stalled. 

The current UN Secretary General Guterres said the investigation “will need to continue with renewed urgency.” He is “deeply committed to doing everything to support the search for the truth. We owe this to Dag Hammarskjöld and the members of the party accompanying him.”

The Legacy of Dag Hammarskjöld

Despite the mystery surrounding his death, the legacy of Dag (ham-er-SHOLD) Hammarskjöld is more crystalized. He posthumously received the Nobel Peace Prize for developing the UN into an effective and constructive international organization, capable of giving life to the principles and aims expressed in the UN Charter. He was the 1st person to receive the award posthumously. 

In 1962, the Dag Hammarskjöld Foundation, a non-governmental organization, was established in memory of the second UN Secretary-General, which aims to advance dialogue and policy for sustainable development and peace. 

Hammarskjöld is buried in Uppsala, Sweden in his family plot, where almost annually, people gather to remember his life, his death, and his legacy of the pursuit of peace. 

And THAT is the incredible, mysterious, and still unconcluded story of the 1961 Ndola United Nations plane crash.