Air Force's mysterious X-37B space plane will return to Earth this week —possibly as early as Tuesday — after 22 months in orbit on a secret mission. The robotic X-37B space plane, also known as the Orbital Test Vehicle, will land at the Vandenberg Air Force Base in California, where Air Force officials are gearing up for its return. "Team Vandenberg stands ready to implement safe landing operations for the X-37B Orbital Test Vehicle, the third time for this unique mission" said Col. Keith Baits, 30th Space Wing commander, in a statement on Friday (Oct. 10). The Air Force has two X-37B space planes in its fleet and has been flying them on secret missions since 2010.