An experimental spacecraft on a secret mission returned to Earth after a two-year mission in space. The craft landed without a problem; however, its mission remains a mystery and the Air Force has not revealed what the experimental mini-shuttle did in space.

The Boeing X-37B landed on Friday Oct. 17 at Vandenberg Air Force Base in California after a 674-day trip in space, according to ABC News. The spacecraft’s mission remains classified.

The X-37B looks like a smaller version of the retired space shuttle; however, it is unmanned. The 29-feet long craft was landed via remote control from earth and will be reused sometime next year for its fourth mission and will be launched from Cape Canaveral, Florida.

"The 30th Space Wing and our mission partners, Air Force Rapid Capabilities Office, Boeing, and our base support contractors, have put countless hours of hard work into preparing for this landing and today we were able to see the culmination of that dedication," Colonel Keith Balts, 30th Space Wing commander, said in a release, according to NBC News.

"I'm extremely proud of our team for coming together to execute this third safe and successful landing. Everyone from our on console space operators to our airfield managers and civil engineers take pride in this unique mission and exemplify excellence during its execution."

The mysterious plane is too small to carry any human passengers but has a truck bed-sized space, which could carry sensors, experiments or weaponry. However, the Air Force has remained silent on the spacecraft’s purpose and mission, intensifying speculation about its mission in space.

The craft was launched on Dec. 11, 2012 aboard an Atlas 5 rocket and it orbited Earth at about 180 miles from the surface.

Watch the X-37B’s remote-controlled landing: