The US Air Force's secret unmanned space shuttle X-37B landed at 1:16 a.m. Pacific time on Friday, concluding its more than 220-day experimental test mission. It was launched from Cape Canaveral Air Force Station, Fla., on April 22.

The X-37B is the United States' first unmanned vehicle to return from space and land on its own. It herlads new opportunities for the manufacturer Beoing in future to focus on unmanned space shuttles which can safely return.

We congratulate the Air Force Rapid Capabilities Office and the 30th Space Wing at Vandenberg Air Force Base on the success of this mission, said Paul Rusnock, Boeing vice president of Experimental Systems and program director for the X-37B. This marks a new era in space exploration, and we look forward to the launch of the second vehicle in 2011.

X-37B Orbital Test Vehicle, which was built by Boeing Co.'s advanced research lab, Phantom Works, was an unmanned shuttle meant for the U.S. Air Force for orbital spaceflight missions.

The X-37B is about 29 feet long with a wing span of about 15 feet and is a reusable robotic spacecraft. It is one-fifth the size of the space shuttle and can draw on the sun for electricity by unfolding its solar panels.

The X-37 began as a NASA project in 1999 and then was transferred to the US Department of Defense in 2004. It had its first flight as a drop test on April 7, 2006.