X-37B spaceplane launch, 2017. This launch, using a Falcon 9 rocket, took place on 7 September 2017 from Launch Complex 39A at NASA's Kennedy Space Center, Florida, USA. Also known as the Orbital Test Vehicle (OTV), this was the fifth orbital mission of this uncrewed spaceplane, which has been in development since 1999. Known as OTV-5, the flight was officially designated as USA-277. This mission landed back on Earth on 27 October 2019 after 780 days in orbit, making it the longest X-37 mission to date. The X-37B is operated by the US Air Force. As of 2019, there have been a total of five OTV launches.