It was used for the first Space Shuttle launch, STS-1, in April 1981. Following the launch of STS-119 in March 2009, it was transferred to the Constellation program. The platform was used only for the Ares I-X and the MLP-1 suffered substantial damage. The canceled Ares I-Y would have used the same MLP. However, the Constellation program was canceled and the MLP was left unused. Following the STS-135, usable parts from the MLP-1 were removed and stored in the Vehicle Assembly Building, with no plans to use the MLP again. In 2021, NASA began rolling out Mobile Launch Platform-1 on Crawler transporter-2 with a concrete ballast on the top to condition the crawlerway to handle the combined weight of the Space Launch System and Orion spacecraft in the future. NASA stated that re-conditioning of the crawlerway will be required periodically in the future, and MLP-1 will be retained for that purpose. MLP-1 will be stored in High Bay 1 of the Vehicle Assembly Building when not in use for crawlerway maintenance. Mobile Launcher Platform-2 Mobile Launcher Platform-2 (MLP-2) (formerly called the Mobile Launcher-2 or ML-2) was used for the uncrewed Apollo 6 mission, followed by three crewed Apollo launches; Apollo 9, Apollo 12 and Apollo 14. It was subsequently used for the launch of Skylab on a Saturn V in 1973. Following the launch of Skylab, ML-2 was the second of the Mobile Launchers to be converted for use by the Space Shuttle. The Launch Umbilical Tower was dismantled and partially reassembled to become the LC-39B Fixed Service Structure (FSS), and the base of the launch platform was modified to accommodate the locations of engines on the Shuttle. The platform was redesignated MLP-2. In total, MLP-2 was used for 44 Shuttle launches, starting in 1983. All of the orbiters except made their maiden flights from MLP-2. It was also the launch site for the ill-fated STS-51L mission, when disintegrated shortly after launch, killing all seven crew members. Following the Space Shuttle retirement, NASA kept the MLP-2 for liquid-propellant rockets, but in January 2021, NASA announced that due to lack of storage space, the massive structure would be demolished. Mobile Launcher Platform-3 The first launch from the Mobile Launcher Platform-3 (MLP-3) (formerly called the Mobile Launcher-1 or ML-1) was the maiden flight of the Saturn V, and the first launch from LC-39, Apollo 4. Following this, it was used for two