Fullerton logged more than 380 hours in space flight, and was a NASA astronaut from September 1969 until November 1986 when he joined the research pilot office at Dryden.

[3] Fullerton entered the U.S. Air Force in July 1958 after working as a mechanical design engineer for Hughes Aircraft Company, Culver City, California.

In 1966, Fullerton was selected for and served as a flight crew member for the Air Force Manned Orbiting Laboratory (MOL) program until its termination in 1969.

After assignment to the NASA Johnson Space Center as an astronaut, Fullerton served on the support crews for the Apollo 14, 15, 16, and 17 lunar missions.

[3] In 1977, Fullerton was assigned to one of the two-man flight crews which piloted the Space Shuttle prototype Enterprise during the Approach and Landing Tests Program at Dryden that same year.

[3] STS-3 landed at Northrup Strip, White Sands, New Mexico, because Rogers Dry Lake at Edwards AFB was wet due to heavy seasonal rains.

[5] Fullerton was one of two NASA pilots who flew the Russian-built Tu-144LL supersonic aircraft used in a joint high speed research program.