Douglas developed and built all types of military planes as well as civilian transport planes. The big breakthrough for Douglas came in the early 1930s when he introduced the DC series of planes. In 1935, Douglas introduced the DC-3, which had 21 to 28 passenger seats, a cruising speed of 180 mph, and could fly 1,000 miles without refueling. By World War II, Douglas made 80% of the commercial aircraft in use. In 1941, Douglas constructed the first of the B-19 bombers for the U.S. Army and produced nearly 30,000 aircraft during World War II.