GLV-6 was the first vehicle in the new west test cell, which Martin had finished installing and checking out in January.

At this time, GLV-5 was still undergoing vertical tests in the other test cell. Because both cells used the same power sources and aerospace ground equipment connections, simultaneous testing was impossible; however, one vehicle could be inspected and prepared for test while the other was being tested. Power was applied to GLV-6 for the first time on May 13. Subsystems Functional Verification Tests continued until June 22.