Douglas B-19 Behemoth (1937-1941): The B-19 was an experimental long-range bomber that was the largest aircraft built in the United States during World War II. In the mid 1930s, the U.S. Army Air Corps asked for a flying battleship able to reach and strike an enemy force thousands of miles from America's coast. The result was the Boeing XB-15 and the Douglas XB-19. When each made its first flight, Boeing's B-15 in 1937, they were the largest aircraft in the United States. Construction of the B-19 took place at the cavernous production hangar at the Douglas plant in Santa Monica, Calif. It had a wingspan of 212 feet, slightly larger than today's Boeing 747-400, and its main landing gear had 24-ply tires that were eight feet in diameter. The B-19's range of 7,700 miles meant it could remain aloft for 55 hours. It had passageways inside the wings so crewmembers could service the engines in flight. The B-19 made its first flight on June 27, 1941, and spent the next six months doing flight tests in Southern California. The December 7, 1941, attack on Pearl Harbor called for special precautions along the California coast, The B-19 was given a coat of camouflage paint and flew its later test flights with its guns armed. In January 1942, the big plane was flown to Wright Field near Dayton, Ohio, where it became a flying laboratory. In 1944 it was fitted with more powerful engines and continued flying test flights. At one point the Army saw potential in the B-19 as a cargo plane and had it modified as a troop transport. However, the B-19 spent most of the war being shuttled from one Midwestern base to another. Although only one was built, the B-19 remained a symbol of American airpower throughout World War II. In 1949 it was declared surplus by the Army and destroyed, though the forward fuselage remained intact and ended up as a real estate office in Tucson, Ariz., for a short time.