The Douglas Skyraider, with its straight, low-mounted, tapered wings, was the only aircraft of its time capable of delivering 8,000 pounds of bombs with dive-bombing precision against such difficult targets as mountain bridges and hydroelectric dams. The first AD-1 Skyraider was delivered in 1946 and named according to the Douglas tradition of starting the names of Navy aircraft with "sky." When the Navy, Marine Corps and Air Force numbering systems merged in 1951, the "AD" series Skyraiders were redesignated as "A" series aircraft. Before production ceased in 1957 twenty-eight variations of Skyraiders were built. These included carrier- or land-based airplanes, day or night attack bombers, and versions for photographic reconnaissance, electronic countermeasures, airborne early warning, utility and search missions. Different configurations carried a pilot in an enclosed cockpit, a pilot and another person (either a radar operator or a co-pilot), and a pilot and two other crew. The AD/A-5 could carry a crew of four, plus four passengers or 12 troops, four stretchers, or 2,000 pounds of cargo. Because of its ability to carry large bomb loads, absorb heavy ground fire and fly for long periods at low altitude, the Skyraider was particularly suited for close-support missions.