The Mobile Launcher Platform (MLP) is one of three two-story structures used by NASA at the Kennedy Space Center to support the Space Shuttle stack throughout the build-up and launch process: during assembly at the Vehicle Assembly Building (VAB), while being transported to Launch Pads 39A and B, and as the vehicle's launch platform. NASA's three MLPs were originally constructed for the Apollo program to launch the Saturn V rockets in the 1960s and 1970s, and remained in service through the end of the shuttle program in 2011 with alterations.}}[citation needed]