Mk-28 Thermonuclear Bomb Casings from the Palomares Incident (1966). On January 17, 1966, a B-52G bomber of the U.S. Air Force’s Strategic Air Command, carrying four Mk-28 thermonuclear bombs, collided with a KC-135 tanker during a midair refueling operation. The aircraft fell into the Mediterranean Sea near the fishing village of Palomares, Spain, killing seven of the 11 crew members. The bomb casing on the left was recovered by navy salvage teams in 2,800 feet of water after a two-and-a-half-month search; the casing on the right was located on land within 24 hours.