NASA sought Air Force support for the shuttle. After the Six-Day War and the Soviet invasion of Czechoslovakia exposed limitations in the United States' satellite reconnaissance network, Air Force involvement emphasized the ability to launch spy satellites southward into polar orbit from Vandenberg AFB. This required higher energies than for lower inclination orbits. The Air Force also hoped that a shuttle could retrieve Soviet satellites and quickly land. It thus desired the ability to land at the Vandenberg liftoff point after one orbit, despite the earth rotating 1,000 miles beneath the orbital track. This required a larger delta wing size than the earlier simple "DC-3" shuttle. However NASA also desired this increased maneuvering capability since further studies had shown the DC-3 shuttle design had limitations not initially foreseen. The Air Force launched more than 200 satellite reconnaissance missions between 1959 and 1970, and the military's large volume of payloads would be valuable in making the shuttle more economical.