Shuttle separates from 747

Before the Enterprise could fly on its own, it first was mated to a Boeing 747 for ground and aerial tests at NASA's Dryden Flight Research Center at Edwards Air Force Base in California. The progression started with three taxi tests in February 1977, and then five flights in which the shuttle was inactive and unmanned. In June and July of that year, still captive to the 747, the shuttle was "active"--a crew on board operated the flight control systems, and did a dress rehearsal for the eventual free flight. Finally, in five flights between August and October, the shuttle was set free.