US Air Force's Secret X37-B Space Plane Lands After 2 Year Mission Robotic X37-B plane was on secret 674 day mission.

 -- The Air Force's secret mini-shuttle has finally returned to earth after spending nearly two years on a classified mission in space, military officials said today.

The X37-B space plane touched down this morning at Vandenberg Air Force Base in California after spending a staggering 674 days aloft.

One of the few things known about the space plane's classified missions is that it can stay in orbit for extended periods of time.

Measuring 29 feet in length and having a 15-foot wingspan, the unmanned re-usable orbital test vehicle looks like a miniature version of NASA's now retired space shuttles.

Like the space shuttle, the X-37B lands on runways, though it does so without pilots at the helm.

The latest flight was the plane's third mission. The X37-B will blast off on its fourth mission sometime next year from Cape Canaveral, the Air Force said.