There were many concept studies leading up to the International Space Station. Early on Boeing was the winning contractor for the NASA/JSC Space Operations Center. Following this, NASA Phase A study contracts were awarded to most major Aerospace companies. For Phase B, space station was divided into Work Packages led by different NASA Centers. After winning the MSFC Common Module Work Package Boeing started building mockups and conducting neutral buoyancy EVA testing at MSFC. Boeing won the Phase C/D for fabrication of the Habitat, Laboratory, Nodes, Airlock, and truss segments. These were built in Huntsville and with the exception of the Habitat Module which never flew, were transported to KSC for launch.