On February 5, 1958, a B-47 bomber dropped a 7,600-pound nuclear bomb into waters off Tybee Island, Georgia after colliding with an F-86 fighter jet. At the time, the quantity of radioactive material, the destructiveness capability of the bomb, and whether it contained a dummy trigger were unclear. The bomb was found to be a 7,600 Mark 15 hydrogen thermonuclear bomb, which has an explosive yield of up to 3.8 megaton, about 190 times more powerful than the Fat Man bomb that destroyed Nagasaki in 1945.
In the incident, a North American F-86 fighter Sabre jet, flown by pilot Lt. Clarence Stewart, accidentally collided with the Boeing B-47 Stratojet, flown by Col. Howard Richardson, during a training mission in which Stewart didn’t see the B-47 on the radar and descended into it. This caused the left wing of the F-86 to be ripped off and damaged the tanks of the B-47. Richardson was concerned the bomb would break loose from his plane and potentially detonate upon landing, so he jettisoned the bomb into waters around Wassaw Sound before safely landing at Hunter Air Force Base outside of Savannah. Stewart ejected and safely landed in a swamp.
A team of 100 Navy personnel equipped with handheld sonar conducted cable sweeps in search of the bomb immediately following the incident, but stopped on April 16 — more than two months after the accident — after failing to find it. Despite the government ending searches, the lost bomb is known among local residents and referred to as the “Tybee bomb.” In 2001, a hydrographic survey of Wassaw Sound revealed that the bomb was buried under five to 15 feet of silt. A 2001 report from the Air Force stated that if the bomb were still intact, the explosive in the bomb would pose no hazard. In 2004, retired Air Force pilot Derek Duke took interest in the matter and detected high radiation 7-10 times higher than normal one mile offshore Tybee, but this was later concluded to be due to naturally occurring minerals. Another government search in this location in 2004 after this discovery around the Wassaw Sound yielded no success.
Initially, experts disputed whether the bomb was nuclear or not. If it contains a plutonium core, it is a fully-functional nuclear weapon. If the core was replaced with a dummy, it would be non-nuclear but still capable of creating a conventional explosion. After the incident, the Air Force assured the public that the nuclear capsule was removed prior to the flight and fitted with a simulated 150-pound cap made of lead. This was widely accepted until documents from a 1966 Congressional testimony were released in 1994 and revealed the weapon was indeed a complete, fully-functional bomb with a plutonium pit. If this is true and the bomb does have a plutonium trigger, an above water explosion would have a fireball with a radius of more than one mile and thermal radiation for up to 10 times that distance.
Additionally, the declassified 1966 report discussed another lost nuclear weapon incident from 1965 in the western Pacific in which a plane had gone over the side of an aircraft carrier in 2,700 fathoms. The aircraft, pilot, and weapon were never found. The United States is reportedly missing six nuclear bombs to date. Although there were rumors that the bomb was retrieved by a Soviet submarine, no evidence has been found to support this, so it is still accepted that the Tybee bomb remains in its original dropped location.