The aircraft loaded with four hydrogen bombs, each of which is a hundred times more powerful than the bomb which obliterated Hiroshima.

Their mission was part of a huge operation called Chrome Dome, which had been running for six years and was a vital part of the United States’ nuclear capability.

In order to provide the superpower with the constant ability to retaliate in the event of a Soviet atomic strike, bombers were continually flown on 24-hour missions all the way across the Atlantic to the east coast of Italy, before turning back to the States.

This meant that if the US President gave the order to strike the Soviet Union, the bombers could swiftly reach the targets over which they could unload their apocalyptic cargoes.

Because of the length of the mission, the B-52 had to be refuelled in the air four times. After turning around over the Adriatic, the plane headed back to her third refuelling point, where she would link up with a huge KC-135 Stratotanker at 31,000 feet above south-eastern Spain.

Just before 10.30 am on January 17, the planes made their rendezvous. With the two aircraft flying at nearly 500 mph, in the refuelling procedure Hell was the right word: the B-52 had overshot and the boom had missed the fuel nozzle in the top of the plane. Instead, the boom had smashed into the bomber with such force that its left wing was ripped off.

Fire quickly spread up the fuel-filled boom and ignited all 30,000 gallons of the tanker’s kerosene, causing it to plummet to the ground. Meanwhile, the bomber started to break up, and the crew did their best to get out of the plane using parachutes.

As for the hydrogen bombs, there was nothing that could be done. In less than two minutes, they would be crashing into the Earth at an enormous speed — potentially destroying much of the regions of Andalucia and Murcia.

 Hundreds of thousands of people could be about to die, and the nuclear fallout would have the capacity to kill millions more all over Europe — not just from radiation poisoning but from cancers for decades to come.

The nuclear payloads of the four American B28 hydrogen bombs mercifully did not detonate when they landed, even though the conventional explosives in two of the bombs did explode, showering some 500 acres around the fishing village of Palomares with three kilograms of highly radioactive plutonium-239.

Despite attempts made at the time by the Americans to clean up the mess, the crash that Monday morning 50 years ago still has ramifications today.

Just last October, U.S. Secretary of State John Kerry agreed to finalise a deal with the Spanish Foreign Minister that calls upon the U.S. to remove and dispose of some 50,000 cubic metres of earth that remains contaminated.

As soon as the crash took place, the residents of Palomares found themselves bombarded with huge scraps of flaming metal. In the words of one five-year-old girl, the sky was ‘raining fire’.

In his elementary school, teacher José Molinero told his pupils to stay inside. A piece of the bomber’s landing gear had smashed down just 80 yards away.

Others had similarly near misses, not least 83-year-old Pedro de la Torre Flores, who was standing with two of his great-nephews that day. One of the four hydrogen bombs fell right in front of them — and blew up.

It was Pedro’s lucky day, though, because the explosion was not a full-scale thermonuclear blast but the detonation of the bomb’s conventional payload. Although Pedro and his nephews were knocked over, they were not vaporised.

So why did the bomb not explode?

The reason is because it had not been armed by the crew, which meant that the electrical circuits required to bring about a full explosion had not been activated. The conventional explosives in hydrogen bombs such as the B28 have to be detonated in a certain sequence in order to bring about the fission of the bomb’s uranium and plutonium, and then the subsequent fusion of the hydrogen atoms that really gives the bomb its terrifying power.

Therefore, when an unarmed nuclear bomb’s conventional payload detonates, the effect is not nuclear armageddon but that of a ‘dirty bomb’ — a conventional explosive that spreads toxic radioactive substances.

What of the remaining three bombs? Miraculously, not one of them caused any damage to people or property.

The second bomb also detonated, although only half of its conventional explosives blew up. The third landed in a dried river bed without exploding, and the fourth fell six miles out to sea.

Still more fortunate, the parachutes on the bombs had failed, which meant they fell with such force that they were largely buried when they detonated, so only a relatively small amount of radioactive plutonium was blown around.

Better still, a breeze took the radioactive particles away from Palomares. No wonder that the village priest said ‘the hand of God’ was at work.

Yet despite the American efforts to eradicate the radioactivity, many residents remain unconvinced that they are safe.

According to one report, around 50 villagers are still carrying plutonium in their bodies, and there is anecdotal evidence that, after the incident, many villagers died of cancers relatively young.

Unfortunately, there is now no way of confirming this, as all the medical records were suppressed and destroyed by the fascist authorities of General Franco, Daily Mail reports.