The BBC has a fine story on this remarkable aircraft. The author postures that the DC-3 may well become the first aircraft to be flying at 100 years old. Boeing has a history on this aircraft here.The Douglas DC-3 carried 21 passengers, was first flown in 1935. It was designed and patented by chief engineer James Kindelberger and designer Arthur Raymond to compete with the Boeing B-247. The B-247 made its first flight in 1933, and was the first all-metal monoplane transport. The B-247 was based on an earlier B-9 bomber. The B-247 was ordered by United Air Lines. The B-247 had twin engines, retractable landing gear and carried 10 passengers in a heated, sound-proof cabin. It was able to cross the country in 20 hours, cruising at 155 mph.
The competing twin-engine Douglas 12-seat DC-1, flew in 1933. The first production version, the DC-2, started scheduled service for Transcontinental & Western Air (later TWA) on Newark-Chicago run in 1934. The DC-2 carried 14 passengers. The success of the DC-2 led to the development of the DC-3 which went into service for American Airlines in 1936.The DC-3 was the first airliner to make commercial air travel profitable. By 1942, 90% of airliners in use were DC-3s. An incredible 11,000 were eventually produced.
During the Second World War the DC-3 was called the Dakota by the British, the C-47 Skytrains by the Air Transport Command, R-4Ds by the US Navy. Though production ceased in 1946, two thousand DC-3s were still in service in the late 1980s.
This will be a tough act to follow. Only the 737 looks like it can come close.