Prior to the "Challenger" disaster, this mission was slated to launch in March 1986 as STS-61-E. Jon McBride was originally assigned to command this mission, which would have been his second spaceflight. He chose to retire from NASA in May 1989 and was replaced as mission commander by Vance Brand. In addition, Richard N. Richards (as pilot) and David Leestma (as mission specialist), were replaced by Guy Gardner and Mike Lounge respectively. 59-year-old Brand was the oldest astronaut to fly into space until Story Musgrave, 61 on STS-80 in 1996, and U.S. Senator John Glenn, 77 when he flew on STS-95 in 1998.