This plane has been flying around in space for nearly a year now. It is owned by US military, and marks the beginning of military operations in space.
It was designed by NASA, built by Boeing’s Phantom Works division and launched at Cape Canaveral back in April 2010, but is now under the control of a 3D Space Squadron, 21st Space Wing, of the US Air Force Space Command in Colorado Springs.
It was announced that it has been designed to make space access more routine, affordable and responsive and will demonstrate various experiments to allow satellite sensors, subsystems, components, and associated technology to be transported into space and back.
Little is known about the plane, but it has been spotted several times operating in low earth orbit. The craft is about 9m long and 4.5 wide. and has a large engine mounted at the rear, but is also powered by solar array and lithium-ion batteries.
There is a lot of secrecy over its specifications, what its mission currently is and what the craft is carrying onboard.
update
Landed at Vandenberg Air Force Base on the 3rd Dec 2010, after being off-ground for 224 days, 9 hours, 24 minutes.