In November 2006 the U.S. Air Force announced it would develop the X-37B from the NASA X-37A. The Air Force version is designated X-37B Orbital Test Vehicle (OTV). The OTV program builds on industry and government investments by DARPA, NASA and the Air Force. The X-37B effort will be led by the Air Force Rapid Capabilities Office and includes partnerships with NASA and the Air Force Research Laboratory. Boeing is the prime contractor for the OTV program. The X-37B can remain in orbit for up to 270 days at a time.