at the SLF via the Shuttle Carrier Aircraft on March 24, 1979. The runway was first used to land a Space Shuttle on February 11, 1984, when Challenger's STS-41-B mission returned to Earth. This also marked the first landing of a spacecraft at its launch site. Prior to this, all Shuttle landings were performed at Edwards Air Force Base in California (with the exception of STS-3, which landed at White Sands Space Harbor) while the landing facility continued testing and Shuttle crews developed landing skills at White Sands and Edwards, where the margin for error is much greater than SLF and its water hazards. On September 22, 1993, Discovery was the first Space Shuttle to land at night at the SLF on STS-51. A total of 78 Space Shuttle missions landed at the SLF. The final landing of a Space Shuttle occurred on July 21, 2011 by Atlantis for STS-135. Discovery and Endeavour took off from the SLF on top of the Shuttle Carrier Aircraft for museums in Washington, D.C. and Los Angeles. Boeing X-37B In January 2014 it was announced that Boeing would lease the Orbiter Processing Facility at Kennedy Space Center to enable the U.S. Air Force to efficiently land, recover, refurbish, and re-launch the X-37B uncrewed spacecraft. In October 2014, NASA signed agreement for the use of the facility, and Boeing upgraded the OPF-1 for the X-37B program. The X-37B (OTV-4 mission) first used Kennedy Space Center's Shuttle Landing Facility on May 7, 2017 at 11:47 UTC. Project Morpheus testing In 2012, NASA's Johnson Space Center's Project Morpheus's first vehicle arrived at KSC. Prior to arrival at KSC and throughout the project, Morpheus vehicle tests were performed at other NASA centers; KSC was the site for advanced testing. Multiple tests, including free flight, were performed at the SLF in 2013–2014. Multiple vehicles and iterations of the vehicles were tested, due to upgrades and damages during this experimental test program. During the August 9, 2012 test at the SLF, a vehicle exploded; no one was injured. Commercial use The SLF has also been used by commercial users. Zero Gravity Corporation, which offers flights where passengers experience brief periods of microgravity, has operated from the SLF, as have record-setting attempts by the Virgin Atlantic GlobalFlyer. The SLF has been the site of high performance automobile testing and speed record attempts. In 2010, NASCAR teams used the facility for vehicle