When Douglas entered the jet age in the late 1950s, they made a mistake by focusing on the short-range market. The early DC-8s, the series -10 and -20, were built for US domestic and continental routes. Its main competitor, Boeing's 707, was sold in many different sizes and variants and was sold in numbers almost twice as high as those of the DC-8.
As a logical consequence, a long-range aircraft was always part of the DC-10 program. The target clients were smaller flag carriers which wanted to grow beyond the DC-8 and 707 and airlines serving long-range routes with lower demand than that of a 747. After defition of the basic DC-10 design, a powerplant was found in the Pratt & Whitney JT9D, the engine which was already available on the 747. A slightly shorter fuselage, slightly larger wings and the characteristic third main gear for the higher weight were the most important changes compared to the DC-10-10. The aircraft was named DC-10-20 and - upon of request of main costumer Northwest Airlines - re-named DC-10-40.
Finally, the aircraft Douglas always wanted for this market was not the DC-10-40. It was the DC-10-30, powered with General Electric's new high-thrust engine, the CF6-50. This engine was developed out of the CF6-6 (the powerplant of the DC-10-10) and became also the most popular engine on the Boeing 747 and Airbus A300B2/B4.
The early pushing of the long-range DC-10 also had a more important impact of the program: The DC-10-30 became available far earlier than Lockheed's projected L-1011-8.4. Before the Northwest order, Douglas was only second in the race with 110 orders (from two costumers, including options) compared to 144 for the TriStar (from five costumers, also including options). The long-range aircraft was pushed into the market, resulting in many sales from european flag carriers. The availability of the long-range aircraft and Lockheed's Rolls-Royce crisis opened the airlines' doors for Mc Donnell - Douglas. The DC-10 was back in race and ready to beat the TriStar.