Nuclear mishaps: The hidden history of America's lost bombs

In the military, soldiers use many terms to communicate with allied units and command. Many of them can be treated "neutrally"—they do not inform about potential danger and are not secret signals to start an attack.

Opposed to these phrases, however, are those which no military personnel would want to hear over radio communication. One of them is "broken arrow," used by the military to describe an accident involving nuclear weapons, though it does not pose a threat of initiating a nuclear conflict.

In the past century, the American military reported "broken arrows" multiple times. Some of the atomic bombs lost years ago are still unaccounted for. To this day, it is unknown what happened to them.

The first "broken arrow" incident occurred seventy-four years ago. Then, the United States Armed Forces decided to carry out a twenty-four-hour airborne mission, which ended in a simulated attack on San Francisco. The Army intended to create conditions akin to those that the sixteen-member Convair B-36 Peacemaker strategic bomber crew would face during a combat flight over the USSR.

The plans fell apart when, after several hours of flying, three out of six engines of the American aircraft malfunctioned. The crew decided to abort the mission and parachute out of the plane. The obstacle, however, was the Mark 4 nuclear bomb (an improved version of Fat Man from Nagasaki) on board.

The pilots decided to drop the bomb in British Columbia, Canada. Fortunately, the unplanned bombing was not tragic in its consequences due to the lack of a plutonium core in the Mark 4. Therefore, a chain reaction could not be initiated, resulting in a conventional explosive detonation. The incident was kept secret for several decades.

Another incident where Americans reported a "broken arrow" was the mysterious disappearance of a Boeing B-47 Stratojet bomber over the Mediterranean Sea. In March 1956, the aircraft took off from MacDill Air Force Base in Florida, bound for a base in Morocco. Along the way, the B-47 was to be refuelled in mid-air twice. The second "stop" was scheduled over the Mediterranean, and after the first successful refuelling, nothing indicated that the plane would vanish.

The bomber did not reach the second tanker. Despite numerous searches, the missing aircraft, its crew, and its payload have never been found. It was carrying two Mark 15 bombs on board.

Shortly after the mysterious disappearance of the B-47 over the Mediterranean, Americans lost another atomic bomb. In a 1958 incident over the Atlantic Ocean, a Boeing B-47 was again involved, participating in manoeuvres simulating the bombing of a Russian city. The exercise programme also included manoeuvres to evade enemy interceptor fighters.

The exercises ended with the bomber colliding with an F-86 fighter jet. The pilot of the latter aircraft managed to eject, but the larger B-47 faced a much bigger problem: a nuclear weapon on board, which attempts to land with were made three times. Eventually, command issued an order to drop the bomb into the ocean, and the bomber was able to return safely to base. The bomb was considered lost and has never been found.

The next decade of the last century was also filled with dangerous "broken arrow" incidents encountered by the U.S. military. In January 1961, a twenty-four-megaton nuclear bomb went missing. It was carried by a B-52 bomber, which reported wing damage during a mission over Goldsboro, North Carolina.

At that time, there were two "nukes" on board the plane. They decided to secure them by executing a controlled drop with parachutes. While one of the bombs completed a safe descent and landed in a location known to the American military, the other fell to the ground in an unknown location but did not explode. It has never been found.

In 1965, another "broken arrow" incident occurred. This time it involved the aircraft carrier USS Ticonderoga, which had an A-4E Skyhawk attack aircraft armed with a nuclear bomb on board.

The aforementioned Skyhawk slid off the carrier, which was sailing near the Philippine Sea, and together with it, the nuclear bomb fell into the water. The weapon has never been found, although the U.S. believes it lies at the bottom of the sea, about 150 kilometres from Japan.

Three years later, another atomic bomb was lost. In 1968, although the exact date is unknown, the Americans reportedly lost an unidentified nuclear weapon. Little is known about this incident, but based on speculation from people associated with the U.S. military, it can be inferred that it involved the disappearance of the nuclear submarine Scorpion. It was sent in 1968 to spy on the Soviet Navy.

Remaining on the topic of nuclear weapons, it is impossible not to mention the bombings of Hiroshima and Nagasaki in 1945. Although there was no question of any pilot error or unexpected failures back then, the history recorded in textbooks today could have been entirely different.

When planning the attacks on Japan, the Americans decided that during the bombing of Hiroshima, the backup target in case of poor visibility would be the city of Kokura. On August 6, 1945, the weather over Hiroshima was favourable, so the backup target remained safe that day.

Soon, however, things were set to change as Kokura was the primary target for the bombing planned for August 9, not Nagasaki, where the Fat Man bomb eventually fell. Due to cloud cover over the city, Boeing B-29 Superfortress pilot, Major Charles Sweeney, set course for Nagasaki, where a nearly 5,000-kilogram nuclear weapon was dropped. Thus, Kokura twice avoided bombing. In both cases, it was due to the weather.

Most "broken arrow" incidents occurred in the 1950s and 1960s, or at least it was then that Americans reported them. Although such events essentially no longer occur today, in 2007, the issue of maintaining safety during manoeuvres with nuclear weapons resurfaced among many experts in the military field.

Seventeen years ago, human error was to blame. During a training flight, a B-52 bomber was accidentally armed with three AGM-129 cruise missiles with nuclear warheads. Training warheads were supposed to be in their place. For nearly two days, no one noticed that the B-52 crew was conducting manoeuvres with armed nuclear weapons on board.