Nuclear problems

It is a toss-up trying to decide which is our biggest existential threat (that it, which problem is most likely to kill off humanity).  Climate change is up there, but as is a nuclear "accident", as explained here.

I kinda suspected that nuclear was not a great idea, but apparently there have been thousands of near misses as ridiculous as these:

• A USAF F-86 jet fighter collided with a USAF B-47 bomber over the American state of Georgia on February 5, 1958. The bomber dropped a nuclear bomb rated at 3.8 megatons (that is roughly 45 times the power of the bomb that destroyed Hiroshima).    It had apparently not been properly maintained and did not function as it should have.   It did not explode.  Had it exploded, it would have incinerated an area as large as the center of New York City – 23rd-59th streets, river to river. And, of course, it could as easily have been dropped accidentally on New York as on Georgia.
• A USAF B-52 carrying two 4-megaton bombs (that is a total of 100 times the size of the bomb that destroyed Hiroshima)  broke apart in mid-air over North Carolina on January 24, 1961. One of the two bombs (in the words of the report) "behaved precisely as a nuclear weapon was designed to behave in warfare: its parachute opened, its trigger mechanisms engaged, and only one low-voltage switch prevented untold carnage." 
• On January 17, 1966, a B-52 collided with a tanker aircraft near the Spanish fishing village of Palomares. The tanker exploded and the bomber broke up, dropping 4 nuclear bombs. The non-nuclear explosives (the "triggers" for the nuclear bombs)  detonated on impact but failed to ignite the nuclear fuel. If they had functioned, as they were supposed to do, they would have obliterated a large part of Spain.  One bomb did not detonate at all, and the fourth bomb apparently floated out to sea under its parachute and was never recovered. 
• At Thule, Greenland on January 23, 1968, a bomber with 4 nuclear weapons aboard crashed; the "trigger" (a conventional bomb) exploded but did not detonate the nuclear material. It luckily malfunctioned.  One bomb was never recovered. 

It looks like it is just dumb luck that we are still alive (for now).