LOMPOC, Calif., Oct. 18 (UPI) -- An unmanned vehicle designed for space flight landed in a California air force base Friday, concluding a nearly two-year mission to conduct experiements while in orbit.

The X-37B Orbital Test Vehicle finished its third mission when it touched down on the tarmac at Vandenberg Air Force Base Friday morning. The vehicle spent 674 days conducting on-orbit experiments, raising its overall time in such missions to 1,367 days, the Air Force said.

The X-37B is "an unmanned space vehicle that will be used by the United States Air Force to explore reusable vehicle technologies in support of long-term space objectives," according to Boeing, the craft's designer.

Both Boeing and the Air Force have called the X-37B "the newest and most advanced re-entry spacecraft" in the world. Managed by the Air Force Rapid Capabilities Office, the craft, which resembles a small space shuttle, was designed for "risk reduction, experimentation and concept of operations development for reusable space vehicle technologies."

The vehicle was launched on an Atlas 5 rocket from Cape Canaveral in Dec. 2012.

The previous two missions were launched in 2010 and 2011, respectively, each ending at Vandenberg Air Force Base.

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Unmanned space plane lands after 22-month mission