The Air Force's mysterious X-37B secret space plane returns to Earth after nearly two years in space.

The X-37B is an unmanned spacecraft that has no human pilot and is operated remotely. It resembles a miniature space craft and has the capability of landing on its own.

It has been in space for exactly 674 days. This is its third mission into space, and it's longest time in space as well.

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The craft landed last October 17 at the Vandenberg Air Force Base in California, the Air Force's 30^th Space Wing announced.

Colonel Keith Balts said that he was extremely proud of the craft and of the team that came together to make its third mission a possibility.

He thanks the mission partners of the 30^th Space Wing such as Air Force Rapid Capabilities Office, Boeing, and our base support contractors.

"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," Balts said.

While it has returned to Earth and been operating for a number of years, people still do not know what the X-37 B exactly does.

Inquiries by NBC News have resulted in the Air Force replying with "no comment." However, to be fair, experimental military-funded space projects aren't really spoken about in public.

An NBC News Report in 2001 though revealed that the Pentagon was promoting the X-37B as a next-generation space bomber.

The report said that they were planning to create a "space operations vehicle" that could be launched from a U.S. base and fire weapons at almost any target on Earth within 90 minutes of a presidential order.

The details of its launch are made public though. Last December 12, 2012, it was launched using an Atlas 5 booster and assumed orbit around 180 miles above the Earth.

Until the Air Force decides to share what the X-37B is really for, it will remain locked in the Vandenberg Air Force Base until it is sent to space once again. 

TagsX-37B, Air Force, Unmanned, Earth