He completed flight training at Pensacola, Florida, Meridian, Mississippi and Kingsville, Texas, receiving his Naval Aviator wings in May 1966.

After A-4 Skyhawk training, he made two Vietnam War deployments aboard the aircraft carrier USS Enterprise with Attack Squadron 113 (VA-113).

He served as a flight instructor in Attack Squadron 125 (VA-125) at Naval Air Station Lemoore, California for two years and transitioned to the A-7 Corsair II aircraft.

[1] Selected by NASA in January 1978, Williams became an astronaut in August 1979, qualified for assignment as a pilot on future Space Shuttle flight crews.

A malfunction in the Syncom spacecraft resulted in the first unscheduled EVA, rendezvous and proximity operations for the Space Shuttle in an attempt to activate the satellite.

STS-34 Atlantis (October 18–23, 1989) was launched from Kennedy Space Center, Florida and returned to land at Edwards Air Force Base, California.

During the mission the crew successfully deployed the Galileo spacecraft, starting its journey to explore Jupiter, operated the Shuttle Solar Backscatter Ultraviolet Instrument (SSBUV) to map atmospheric ozone, and performed numerous secondary experiments involving radiation measurements, polymer morphology, lightning research, microgravity effects on plants, and a student experiment on ice crystal growth in space.