Secretive Space Plane Left in 2017, Just Returned

The Air Force's mystery space plane is back on Earth, following a record-breaking two-year mission. The X-37B landed at NASA's Kennedy Space Center in Florida Sunday, per the AP. The Air Force is mum about what the unmanned plane did in orbit after launching aboard a SpaceX rocket in 2017. The 780-day mission sets an endurance record for the reusable test vehicle, which looks like a space shuttle but is one-fourth the size at 29 feet. Officials say this latest mission successfully completed its objectives, without specifying them. Experiments from the Air Force Research Laboratory were aboard. This was the fifth spaceflight by a vehicle of this sort. No. 6 is planned next year with another launch from Cape Canaveral. (The previous record was 718 days.)