Between 1982 and 1992, NASA launched 11 shuttle flights with classified payloads, honoring a deal that dated to 1969, when the National Reconnaissance Office—an organization so secret its name could not be published at the time—requested certain changes to the design of NASA’s new space transportation system. The NRO built and operated large, expensive reconnaissance satellites, and it wanted a bigger shuttle cargo bay than NASA had planned. The spysat agency also wanted the option to fly "once around" polar missions, which demanded more flexibility to maneuver for a landing that could be on either side of the vehicle's ground track.

"NRO requirements drove the shuttle design," says Parker Temple, a historian who served on the policy staff of the secretary of the Air Force and later with the NRO's office within the Central Intelligence Agency. The Air Force signed on to use the shuttle too, and in 1979 started building a launch pad at Vandenberg Air Force Base in northern California for reaching polar orbits. Neither the Air Force nor the NRO was ever comfortable relying exclusively on NASA’s vehicle, however. Delays in shuttle launches only increased their worry; even before the 1986 Challenger accident, they were looking for a way off the shuttle and back onto conventional rockets like the Titan.