The C-47 was a military adaptation of the Douglas DC-3, a twin-engine low-wing monoplane with retractable landing gear that quickly dominated the infant commercial airline industry from its first appearance in 1935. With war clouds gathering over Europe, the Army Air Forces ordered military versions of the DC-3 in 1939, and the first of these, the C-53 Skytrooper, entered production in October 1941. The C-53 Skytrooper was developed as a dedicated troop transporter and for dropping paratroops. It was very similar to the C-47 Skytrain, but without the reinforced cargo floor, large cargo door and hoist attachment of the dual purpose C-47. In all, some 250 C-53s were produced.

As a supply plane, the C-47 could carry up to 6,000 pounds of cargo. It could also hold a fully assembled jeep or a 37 mm cannon. As a troop transport, it carried 28 soldiers in full combat gear. Finally, the C-47 could tow two CG-4 Waco assault gliders or one of the larger British Horsa gliders. As an aerial ambulance, the C-47 could carry 18 stretcher cases and a medical crew of three. Seven basic versions were built, and the aircraft was given at least 22 designations, including the AC-47D gunship, the EC-47 electronic reconnaissance aircraft, the EC-47Q antiaircraft systems evaluation aircraft and the C-53 Skytrooper.

Every branch of the U.S military and all the major allied powers flew it. The U.S. Navy version was the R4D. The British and the Australians designated it the Dakota (a clever acronym composed of the letters DACoTA for Douglas Aircraft Company Transport Aircraft). The aircraft operated from every continent in the world and participated in every major battle. By the end of World War II, more than 10,000 had been built. For all of its official and unofficial names, it came to be known universally as the Gooney Bird; General Dwight D. Eisenhower, Supreme Commander of Allied Forces in Europe, termed it one of the most vital pieces of military equipment used in winning the war.

C-47s remained in active military service long after the end of World War II. They played a critical role in the 1948 Berlin Airlift and saw action in the Korean and Vietnam wars.