Palomares incident: A B-52 bomber collides with a KC-135 Stratotanker over Spain, killing seven airmen, and dropping three 70-kiloton nuclear bombs near the town of Palomares and another one into the sea.

The Palomares incident occurred on 17 January 1966, when a United States Air Force B-52G bomber collided with a KC-135 tanker during mid-air refueling at 31,000 feet (9,450 m) over the Mediterranean Sea, near the Spanish village of Palomares in Almería province. The collision destroyed the tanker, killing all four crew members, and caused the bomber to break apart, resulting in the deaths of three of its seven crew members. The B-52G was participating in Operation Chrome Dome, a Cold War airborne alert mission involving continuous flights of nuclear-armed bombers.

The Boeing B-52 Stratofortress is an American long-range subsonic jet-powered strategic bomber. The B-52 was designed and built by Boeing, which has continued to provide support and upgrades. It has been operated by the United States Air Force (USAF) since 1955 and was flown by NASA from 1959 to 2007. The bomber can carry up to 70,000 pounds (32,000 kg) of weapons and has a typical combat range of around 8,800 miles (14,200 km) without aerial refueling.

The Boeing KC-135 Stratotanker is an American military aerial refueling tanker aircraft that was developed from the Boeing 367-80 prototype, alongside the Boeing 707 airliner. It has a narrower fuselage and is shorter than the 707. Boeing gave the aircraft the internal designation of Model 717. The KC-135 was the United States Air Force (USAF)'s first jet-powered refueling tanker and replaced the KC-97 Stratofreighter. The KC-135 was initially tasked with refueling strategic bombers, but it was used extensively in the Vietnam War and later conflicts such as Operation Desert Storm to extend the range and endurance of US tactical fighters and bombers.

The B28, originally Mark 28, was a thermonuclear bomb carried by U.S. tactical fighter bombers, attack aircraft and bomber aircraft. From 1962 to 1972 under the NATO nuclear weapons sharing program, American B28s also equipped six Europe-based Canadian CF-104 squadrons known as the RCAF Nuclear Strike Force. It was also supplied for delivery by UK-based Royal Air Force Valiant and Canberra aircraft assigned to NATO under the command of SACEUR. In addition, certain U.S. Navy carrier based attack aircraft such as the A3D Skywarrior, A4D Skyhawk, and A3J Vigilante were equipped to carry the B28.