Under the Commercial Crew Program, SpaceX and Boeing were selected to develop U.S.-based crew transportation capabilities that would be certified by NASA to meet human-rating requirements and begin routine flights to the International Space Station. The SpaceX Crew Dragon received its certification in 2020 and has flown 12 crewed missions to and from the Station since that time. The Boeing Starliner, however, is uncertified as its three flight tests have uncovered a significant number of unexpected issues with varying levels of mission risk that remain.
