The U.S. Space Force's robotic X-37B space plane has been aloft for more than 900 days on its current mission, the sixth for the X-37B program. The U.S. military's X-37B robotic space plane just passed 900 days in orbit on its latest hush-hush mission, adding to the program's flight-duration record. The current mission is the sixth for the X-37B program and is therefore known as OTV-6 ("Orbital Test Vehicle 6"). It launched on May 17, 2020, from Cape Canaveral Space Force Station in Florida, and it's unclear when it will end. OTV-6 is the first X-37B flight to use a...