With his hugely successful commercial aircraft, including the legendary DC-3, founder Donald W. Douglas led his company to the forefront of aircraft manufacturers starting in the 1930s. "Depend on Douglas" was the company motto, and the company founder stood behind it with his name. Between 1945 and 1960, the DC-4, DC-6, and DC-7 four-engine "Big Prop" models were flown by many of the world's most famous commercial airlines of the era, including Pan Am, United, American, Eastern, Delta, KLM, BOAC, Swissair, SAS, Air France, Alitalia, and Japan Air Lines. This is the history of the design, development, and operational use of the Douglas Big Props, including technical specifications and details of military variants. Period photographs bring to life the fascinating history of these early, and influential, commercial airliners, some of which still fly today.