Mission is still classified
The USAF launched the mysterious X-37B spacecraft on December 11 of 2012 for its OTV-3 mission. It has been almost a year now and the spacecraft is still in orbit. Exactly what the mission of the X-37B is we don’t know. The particulars of the spacecraft and its mission are classified.
This is the third mission for the X-37B and the second for this specific spacecraft reports Space.com. The X-37B in orbit right now was also in space for mission OTV-1 and spent 225 days in orbit. Another X-37B went up for OTV-2 mission and spent 469 days in space.
The X-37B spacecraft are similar to the retired space shuttle fleet, but are completely unmanned. They are also significantly smaller.