A robotic miniature space shuttle on a classified mission for the U.S. Air Force marked its 500th day in orbit on Friday, with no word about when and where the space plane will land.
PHOTOS: Military Mini-Shuttle Completes Secret Mission
The X-37B, one of two vehicles comprising the Orbital Test Vehicle, or OTV, program, blasted off aboard an unmanned Atlas 5 rocket from Cape Canaveral Air Force Station on Dec. 11, 2012.
Five hundred days later, it's still in orbit, eclipsing by wide margin the 244-day flight of the last X-37B mission.
The Air Force did not immediately respond to a request for comment about the milestone, nor how much longer it planned to keep OTV-3 in space.
By the time it returns, the program may have a new home base.
NEWS: Secret Mini-Shuttle Lands in California
Boeing is investing in a mothballed space shuttle processing hangar at the Kennedy Space Center to refurbish the 29-foot long X-37B vehicles in Florida. Previously, the vehicles launched from Florida but landed and were prepared for flight at Vandenberg Air Force Base in California.