William Hewitt Phillips, known more familiarly as Hewitt Phillips, was born in Merseyside, England, in 1918, but moved with his parents at age two to the United States. He studied aeronautical engineering at the Massachusetts Institute of Technology (MIT), obtaining an S. B. degree in 1939 and an S.M. in 1940.

In July 1940, Phillips entered commenced service with the National Advisory Committee for Aeronautics (NACA), where he was assigned to the Flight Research Division at Langley Research Center (Hampton, Virginia), specializing in the study of aircraft flying qualities and stability. Within this broader assignment, Phillips' task involved the improvement of World War II military aircraft flying qualities. Following the war, Phillips' research related to the development of jet-powered fighter airplanes, supersonic airplanes, stability augmentation and its effect on pilot control, automatic control, and gust alleviation. In 1947, Phillips had married Viola Ohler, then head of Langley's editorial office. The couple had three children.

As the U. S. space program commenced, Phillips became chief of the Space Mechanics Division, supervising research in the areas of space rendezvous, navigation, and lunar landing and developing flight simulators for the Gemini and Apollo programs. To train astronauts for lunar landings, Phillips developed the Lunar Landing Facility. He later served as an analyst and consultant in the development of the space shuttle.

Phillips retired from NASA in February 1979 but continued in the position of distinguished research associate, performing original research on solar-powered aircraft, propellers, airfoil design and wind-tunnel studies of the use of canard surfaces for the space shuttle.