A top-secret space plane landed Friday at an Air Force base on the Southern California coast. The plane spent nearly two years circling Earth on a classified mission. Known as the X-37B, it resembles a mini space shuttle. It safely touched down at 9:24 a.m. Friday, officials at Vandenberg Air Force Base said. Just what the plane was doing during its 674 days in orbit has been the subject of sometimes spectacular speculation. Several experts have theorized it carried a payload of spy gear in its cargo bay. Other theories sound straight out of a James Bond film, including that the spacecraft would be able to capture the satellites of other nations or shadow China's space lab. In a written release announcing the return of the craft, the Air Force only said it had been conducting "on-orbit experiments." via Yahoo News.