Gemini VIII was launched on March 16, 1966, carrying astronauts Neil Armstrong (command pilot) and David Scott. They accomplished the first docking of two spacecraft in history, after rendezvousing with an unmanned Agena vehicle launched earlier the same day. Shortly after docking, one of the Gemini's attitude control thrusters malfunctioned and the combined vehicles began to buck. The crew undocked from the Agena, but the spacecraft began to roll wildly, eventually reaching one revolution per second. Armstrong and Scott used the Re-entry Control System to stop the roll; mission rules then forced them to make an emergency landing in the Pacific less than twelve hours into a three-day mission.

The Gemini VIII spacecraft was later used by the manufacturer, McDonnell, in ground testing for the Defense Department's Manned Orbiting Laboratory program. In 1972 McDonnell gave the Gemini VIII to the Smithsonian for NASA.