The first long-range version fitted with Pratt & Whitney JT9D engines. Originally designated "DC-10-20", this model was renamed DC-10-40 after a special request from Northwest Orient Airlines: the aircraft was much improved compared to its original design, with a higher MTOW (on par with the Series 30) and with more powerful engines. The airline's president wanted to advertise that he had the latest version. The company also wanted its aircraft to be equipped with the same engines as its Boeing 747s for fleet commonality.