B43

Development of the B43 thermonuclear bomb began in 1956, with production starting in 1959. The weapon entered service in April 1961, and production concluded in 1965 with 2,000 units manufactured.

The B43 was an air-dropped, variable-yield thermonuclear gravity bomb utilizing the Tsetse primary design for its fission stage. It was produced in two variants, Mod 1 and Mod 2, each offering five yield options ranging from 70 kilotons to 1 megaton of TNT. Delivery options included airburst, ground burst, free fall, contact, or laydown delivery, and the weapon could be released at low altitudes. Certain variants featured a ribbon parachute for parachute-retarded delivery.

The weapon was deployed by the United States on various fighter, bomber, and attack aircraft, including the A-3, A-4, A-5, A-6, A-7, B-47, B-52, B-58A, F-100, F-105, F-4, F-104, FB-111A, F-15E, F-16, and F/A-18. The B-1B Lancer was also intended to carry the weapon, though its type-approval remains unconfirmed. Under NATO agreements, the B43 was supplied to the United Kingdom for Royal Air Force Canberra and Valiant aircraft under SACEUR command. It was also carried by Canadian CF-104 jets stationed in Germany between June 1964 and 1972.

The B43 was never used in combat. On 5 December 1965, a B43 weapon was lost in an accident off the coast of Japan. An A-4E Skyhawk of Attack Squadron VA-56 embarked on the USS Ticonderoga (CVA-14) rolled off an elevator into the Pacific Ocean near Kikai Island, Kagoshima Prefecture. The pilot, aircraft, and bomb were never recovered. The incident was disclosed in a 1989 United States Department of Defense report.

The B43 was phased out during the 1980s, and the final units were retired in 1991, replaced by the B61 and B83.