Here’s what you’ll learn when you read this story:

• Operation Chrome Dome, a U.S. Air Force Cold War mission, flew continuous B-52 bombers around the world, armed with thermonuclear bombs that could attack the Soviet Union at a moment’s notice.
• On January 17, 1966, a B-52G bomber carrying four thermonuclear bombs crashed into a KC-135 tanker over the skies of Palomares, Spain.
• Thankfully, none of the bombs were armed but the accident required months of clean-up and eventually a years-long lawsuit in the 21st century, enabling veterans who participated in that clean-up to receive appropriate benefits and health care.

Gradually developed in the 1950s and established as doctrine in the 1960s, the U.S. nuclear triad forms the backbone of the Pentagon’s nuclear deterrence strategy. One leg of that triad—alongside missile silos and submarines—is the aerial threat posed by strategic bombers. Today, those bombers no longer fly constant patrols, but from 1961 to 1968, B-52s carrying humanity’s most destructive weapons regularly flew strategic routes within easy striking distance of the Soviet Union in a mission known as Operation Chrome Dome.

Although flying bombers around the clock might have seemed like a necessary measure at the time, it was far from a safe one. That would become abundantly clear one morning over the skies of Spain at the height of the Cold War. On January 17, 1966, a U.S. B-52G bomber flying the southern route (which essentially meant traveling across the Strait of Gibraltar, cruising over the Mediterranean Sea, and angling upward along Italy's eastern coast above the Adriatic Sea) collided with a KC-135 refueling tanker at approximately 10:30 a.m. local time. Such tragedies can occur during refueling maneuvers, but this particular accident was especially alarming because the B-52 happened to be carrying four thermonuclear bombs.

Three of the bombs landed near the town of Palomares, on the southeastern coast of Spain, while a fourth bomb fell into the waters of the Mediterranean. Within hours, around 1,600 U.S. military personnel filled the remote fishing village, because while none of the bombs were armed, two of the weapons had formed craters and scattered plutonium across the tomato fields of Palomares.

“It was just chaos,” John Garman, a then-23-year-old military police officer who surveyed the crash site only a few hours after the accident, said in an interview with The New York Times in 2016. “Wreckage was all over the village. A big part of the bomber had crashed down in the yard of the school.”

According to History.com, 1,400 tons of radioactive soil and vegetation were eventually shipped to the U.S. for safe disposal. But while three of the bombs were accounted for on land, the fourth had vanished into the Mediterranean Sea. What followed was one of the most extensive underwater recovery operations in history. The 80-day search involved some 33 Navy vessels, three thousand personnel, and the deep-sea submersible Alvin. A local fisherman, Francisco Simó Orts, had watched the bomb descend into the water on a parachute, and his eyewitness account helped narrow the search area. The Alvin finally located the weapon on a steep underwater slope at a depth of roughly 2,500 feet. But the ordeal wasn't over. During the first recovery attempt, a cable snapped and the bomb slid deeper into an underwater canyon. It was lost again for nine more agonizing days. It wasn’t until April 7, 1966, that the bomb was finally brought to the surface. Miraculously, it was dented but intact, with no radiation leakage.

Of the 11 crew members in the two aircraft that were involved in the accident, seven were killed. But no villagers on the ground were killed or injured in the radioactive accident. However, for decades afterward, the 1,600 or so U.S. veterans who participated in the cleanup fell sick, often with various cancers related to radiation exposure. Soldiers eventually filed a class-action lawsuit against the U.S. Department of Veterans Affairs, which denied that there was any radiation risk at the site. Eventually, Congress passed the Palomares Veterans Act in 2022, offering disability and health care for surviving Palomares veterans and certain benefits to family members of deceased veterans as well.

Operation Chrome Dome didn’t last long after the Palomares Incident because almost exactly two years later, another thermonuclear bomb-laden B-52 bomber crashed into North Star Bay near Thule Air Base in Greenland. In response, the United States Air Force Strategic Air Command immediately suspended the operation indefinitely.