Capping a 15-month clandestine military mission circling the planet, the Pentagon's miniature spaceplane, one quarter the size of NASA's now-retired space shuttle, returned to Earth just after dawn Saturday for a pinpoint touchdown at Vandenberg Air Force Base.

The powerless glider's approach and landing used Vandenberg's three-mile-long concrete runway once envisioned to support manned space shuttles returning from polar-orbiting military flights. The base is located on California's Central Coast about 150 miles northwest of Los Angeles.

"Similar to OTV-1, the vehicle will go through post-landing assessments and refurbishment and lessons learned from that will be incorporated into the next mission," said Maj. Tracy Bunko, an Air Force spokeswoman.

Watch a video of the landing and see a collection of post-landing photos.

The official duration for OTV-2 was 468 days, 13 hours and 2 minutes on a voyage that circled the globe more than 7,000 times. The single-mission numbers surpassed the flight time amassed and orbits accumulated by any of the individual space shuttles in their reusable lives. Discovery had the fleet-leading credentials at 365 days and 5,800 orbits on 39 trips to space.

The marathon OTV-2 flight also lasted twice as long as the program's maiden mission in 2010.

Vandenberg officials said its personnel had conducted extensive, periodic training to stay ready to receive the spaceplane at a moment's notice. Range Safety personnel had the duty to destroy vehicle if it had deviated from prescribed boundaries, but all went according to plan Saturday.

"Team Vandenberg has put in over a year's worth of hard work in preparation for this landing and today we were able to see the fruits of our labor," said Col. Nina Armagno, 30th Space Wing commander. "I am so proud of our team for coming together to execute this landing operation safely and successfully."

Launched atop an Atlas 5 rocket from Cape Canaveral on March 5, 2011, shrouded inside the booster's nose cone for the flight through the atmosphere, the winged craft was inserted into low-Earth-orbit where it operated in secret to carry out a research mission with a classified payload.

Its pickup truck-size cargo bay, seven feet long and four feet wide, could have been filled with equipment being exposed to the harsh environment of space for proof testing or could have contained experimental instruments intended for use by future military and reconnaissance satellites. The craft's unique capability to drop from orbit and land on a runway allows technicians to get their hands on the hardware after it spent more than a year in space.

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Air Force's mini space shuttle returns after 468-day flight