Johnson was the first USAAF fighter pilot in the European theater to surpass Eddie Rickenbacker's World War I score of 26 victories. He finished his combat tour with 27 kills. He was later credited by the Eighth Air Force claims board with a 28th victory when a "probable" was reassessed as a "destroyed", then reduced back to 27 when a post-war review discovered that the Eighth Air Force had inadvertently switched credits for a kill he made with a double kill made by a fellow 56th Fighter Group pilot, Ralph A. Johnson, on November 26, 1943, a day when Robert Johnson aborted the mission after takeoff. (Their army serial numbers were also nearly identical, O-662216 and O-662217.)