I am now half way through the book referenced below (which isn't exactly new, it turns out. More like 2011), and the picture is even murkier. I'll report when I'm done with it.
In September, 1961, a guy named Dag Hammarskjöld died in a plane crash in Africa. Lots of people died in Africa, that year, many of them from the effects of post-colonialism, otherwise known as "Goodbye and thanks for all the money". Mr. Hammarskjöld's death would be just one among many except for his being Secretary General of the United Nations. He was going to take charge of a situation that the UN's inexperience with proxy wars had created: UN troops were in actual offensive and defensive combat with the forces of a state, Katanga; it was trying to secede from the rest of what had been the Belgian Congo. The rebels were mostly anti-communists, and the government they were trying to get away from were to some extent honeyed-up to the the Soviet Union. After the crash, many lengthy investigations took place, and nobody ended up pointing a finger at a cause -- hostile action, malfunction, operator error, weather: nobody could say conclusively what happened.
Now, apparently spurred on by a book that collects all sorts of conspiracy hypotheses and previously-suppressed data, the UN is opening or pushing to open a new investigation. But what's interesting to me is that one theory (and a pretty good one, based on limited knowledge and data) is that Hammarskjöld's DC-6 was shot down by another aircraft, and the aircraft may have been a relatively modern Fouga Magister jet trainer, flown by a Belgian mercenary, Jan van Risseghem. Mr. van Risseghem was a WWII veteran, an accomplished pilot, and in charge of the Katangan "air force". One source says he was "the pilot" of the rebel leader, Moise Tshombe.
It took me most of the morning to search my way through the various threads of this thing, and all I can conclude is the classic "we need more data". There are a number of smoking guns, including a radio transmission from someone flying a plane at the time and more or less the place, telling someone else that he saw a plane, yes it's the right plane, I'm making a run on it, (sound of guns,) I hit it. That sounds a touch glib, but that's what's claimed.