The Boeing X-20 Dyna-Soar was a United States Air Force (USAF) program to develop a spaceplane that could be used for a variety of military missions, including aerial reconnaissance, bombing, space rescue, satellite maintenance, and as a space interceptor to sabotage enemy satellites. The program ran from 24 October 1957, to 10 December 1963, cost US$660 million, and was cancelled just after spacecraft construction had begun.