…On December 5, 1965, U.S. Navy Lt. Douglas Webster was supposed take an A-4E Skyhawk loaded with a nuclear bomb into the sky. On the USS Ticonderoga aircraft carrier, stationed in the Philippine Sea about 70 miles from Okinawa, Japan, the crew loaded the weapon onto the vehicle and Webster got into the cockpit. The crew then pushed the plane to an elevator that would bring it up to the flight deck.

The plan was for Webster to fly around, then land back on the aircraft carrier where the crew would unload the weapon. Webster never made it into the air. The Skyhawk rolled out of the elevator and the crew began to frantically wave at Webster, calling on him to hit the breaks. “According to testimony during the post-incident Board of Inquiry investigation, the pilot seemed oblivious to the whistles and was looking down,” Chief Petty Officer Delbert Mitchell, who was on the crew that loaded the bomb onto the Skyhawk, told the U.S. Naval Institute in 2019.

Navy crew desperately tried to stop the Skyhawk, but they only managed to pivot it in place as it rolled inevitably to the side of the carrier. It hit the netting on the side of the elevator, broke through it, and fell into the ocean. The nuke was armed. “We never saw Lieutenant Webster after he climbed into the cockpit or knew what efforts he might have attempted to get out of the Skyhawk, but we were stunned to witness a plane, pilot, and nuclear weapon fall into the ocean,” Mitchell said.

Mitchell and the rest of the ship looked into the ocean and watched as the Skyhawk sank into the ocean, its landing gear sticking straight up into the air. Efforts to save Webster and recover the nuclear bomb started immediately. The Navy called in other ships to aid with the search but discovered no sign of the missing nuke or plane—they only ever found Webster’s helmet.

The Navy did not talk about the incident for decades. It reported the incident to Congress a year later when the Joint Committee on Atomic Energy was studying the shocking number of Broken Arrows, but the general public wouldn’t learn that America had lost an active nuke off the coast of Japan until 1989.

From car keys to glasses to rifles, everyone misplaces something important from time to time. But when you’re the U.S. government, sometimes that important thing is a superweapon that is designed to destroy cities and kill millions of people.

Over the decades, the U.S. military has had 32 nuclear accidents, also called “Broken Arrow” incidents. These incidents include accidental launches, radioactive contamination, loss of a nuclear weapon or other unexpected events involving nuclear weapons. Luckily, of those 32 accidents, there were only six U.S. nuclear weapons that could not be located or recovered, and of those six weapons, only one was capable of a nuclear detonation when it was lost.

While even one missing nuclear weapon sounds scary, it’s worth noting that the Soviet Union lost far more during the Cold War, often due to submarines sinking with a dozen or more nuclear missiles on board.

“Compared to the Soviet Union, the U.S. record is pretty impressive, given how many nuclear weapons it has operated and transported everywhere over the years,” Hans Kristensen, director of the Nuclear Information Project for the Federation of American Scientists, told Task & Purpose.

In fact, U.S. government agencies often go to great lengths to secure lost weapons. One such incident occurred on Jan. 17, 1966, when a B-52 and a KC-135 refueling tanker collided over southern Spain and scattered four B-28 thermonuclear bombs around the fishing village of Palomares. The conventional explosives for two of the bombs exploded, but the nuclear components did not detonate because they were not armed. The U.S. military sent troops to pick up the undetonated one that fell on land, clean up the radioactive pieces scattered by the two which detonated, and find the fourth which landed in the sea. The U.S. government even dispatched a submarine to find the one in the Mediterranean Sea. Called ‘Alvin,’ the small deep-ocean sub was high-tech for its time, but the crew nearly died when the sub was almost entangled in the parachute that was still attached to the bomb on the ocean floor. Meanwhile, the service members who helped find the landward bombs and clean up the wreckage also developed cancers which they say are linked to that mission 56 years ago.

Considering the extent to which the U.S. looks for lost nukes like it did in Palomares, the stories behind the five instances where recovery crews could not locate or recover weapons are extraordinary. Below is a list of those five accidents, one of which resulted in two missing nuclear weapons. Keep in mind that in all but one, the lost nuclear weapons did not include the pit or capsule that contains the components for triggering a nuclear detonation. That means we can all sleep a little easier knowing those weapons cannot blow up a city. However, the U.S. government still classifies those pit-less devices as nuclear weapons: sophisticated, expensive machines that at the time were closely-guarded tools of mass destruction. And there are many more out there from other governments like the Soviet Union which may never be found.