The EC-121s were designed for detection of aircraft flying over water and the ground clutter (spurious signal returns off of terrain features such as mountains) caused interference with their radar pictures. The crews, however, were experienced in tracking Soviet aircraft over Cuba and had developed a technique whereby an EC-121 flying at 50 to 300 feet above water could bounce a signal from its bottom-mounted APS-95 Search radar off the surface of the water and detect aircraft at medium altitudes out to 150 miles. Operating in pairs, one Big Eye EC-121 flew a 50-mile race track pattern approximately 30 miles offshore (Alpha orbit), with the orbit's center at . The second one flew a track at 10,000 feet (Bravo orbit) farther from the coast, acting as a spare for the Alpha EC-121.