The U.S. Air Force's X-37B Orbital Test Vehicle 4 is seen after at NASA 's Kennedy Space Center Shuttle Landing Facility in Florida May 7, 2017. Managed by the Air Force Rapid Capabilities Office, the X-37B program is the newest and most advanced re-entry spacecraft designed to perform risk reduction, experimentation and concept of operations development for reusable space vehicle technologies. (U.S. Air Force courtesy photo)