Atlantis flew the final classified military deployment of 1990 in November, a mission wrapped in the usual secrecy. The crew of five is understood to have deployed a data-relay satellite serving reconnaissance systems, working through a flight plan the public was never shown.
The mission ended with Atlantis returning to the Kennedy launch site in Florida, only the second Shuttle landing there and a rarity in an era when weather usually sent orbiters to the reliable lakebeds of California. The Florida touchdown saved the time and cost of ferrying the orbiter cross-country, an efficiency NASA was keen to prove out even as the run of dedicated Defense flights was winding down.
This November 1990 flight was the last of the classified missions to be conducted under full security restrictions, and it was unusual even by those standards: the launch was moved from Florida's usual arrangements at short notice, the orbit was low, and Atlantis came home to Kennedy after less than five days.
The payload has never been confirmed. Analysts who tracked the vehicle reported an object that manoeuvred repeatedly after release, consistent with a reconnaissance satellite adjusting its orbit, and several accounts suggest an on-board problem forced the crew to spend an extra day sorting out a deployment that had not gone to plan.
By this point the military relationship was already unwinding. The post-Challenger decision to move national security payloads back to expendable rockets was working through the manifest, and the Air Force was building the Titan IV specifically so it would never again depend on a crewed vehicle to orbit its most important spacecraft. Two more dedicated flights followed, and then the arrangement ended.
