The U.S. military's experimental X-37B space plane landed on Sunday at NASA’s Kennedy Space Center in Florida, completing a classified mission that lasted nearly two years, the Air Force said. The unmanned X-37B, which resembles a miniature space shuttle, touched down at 7:47 a.m. EDT (1147 GMT) on a runway formerly used for landings of the now-mothballed space shuttles, the Air Force said in an email.