The U.S. Air Force tweeted Sunday morning that “The Air Force #X37B #OTV4 has returned from orbit and landed safely at @NASAKennedy.”

The X37B is a secret military unmanned mini-space shuttle, which as been orbiting the Earth for nearly two years on its fourth flight. Multiple media outlets reported that the 29-foot-long spacecraft's return caused a sonic boom that rattled central Florida and could be heard as far away as Tampa and Fort Myers. Sunday's landing sparked a flurry of tweets and questions about the sonic boom, with The Orlando Sentinel reporting that before the landing, officials had refused to confirm rumors of a pending return to Florida. “The ability for this fourth mission to attempt a return to the runway at Kennedy follows three highly successful, completely autonomous deorbit, entry, and landing sequences of the first three X-37B flights, which all ended with precise touchdowns at the runway at Vandenberg Air Force Base, CA,” the site said. U.S. Air Force

The spacecraft are believed to fly as orbital test beds for advanced technology sensors and other systems but the program is classified, and the Air Force provides almost no details on the nature of the space plane's missions, what might have been accomplished or when the reusable craft might fly again. OTV-1 flew the program's first and third missions while OTV-2, flew the second and fourth, which began with launch atop an Atlas 5 rocket at the Cape Canaveral Air Force Station on May 20, 2015.
The United States Air Force's unmanned spacecraft X-37B successfully lands at Kennedy Space Center's Shuttle Landing Facility in Merritt Island, Florida, after spending a record-breaking 718 days in orbit. The landing was responsible for reports of sonic booms across central Florida.