Stratolaunch LLC is an American aerospace company providing high-speed flight test services. It was originally formed in 2011 to develop a new air-launched space transportation system, with its corporate headquarters located in Seattle, Washington. The company and development project were officially announced in December 2011 by Microsoft co-founder Paul Allen and Scaled Composites founder Burt Rutan, who had previously collaborated on the creation of SpaceShipOne. The project originally had three primary components: a carrier aircraft being built by Scaled Composites, a multi-stage payload launch vehicle which was to have been launched at high altitude into space from under the carrier aircraft, plus a mating and integration system by Dynetics. Ultimately, only the carrier aircraft was fully developed by the time of Paul Allen's death in late 2018. The carrier aircraft first flew in April 2019, at the Mojave Air and Space Port, reaching 15,000 ft and 165 kn in a 2 h 29 min flight.