Popularly known as a robotic space plane, the Boeing X-37B is a U.S. unmanned vertical-takeoff, horizontal-landing space vehicle that is capable of orbiting the earth for 250 days or more. The X-37B looks similar to NASA's retired space shuttle, but much smaller. It is about 29 feet long and 15 feet wide, with a payload bay about the size of a pickup truck bed. Two X-37B vehicles could fit inside the payload bay of a space shuttle. The space plane's orbital longevity is enabled by its solar array, which generates power to sustain long-term operations after deployment from its payload bay.

The X-37B is operated by the United States Air Force for orbital spaceflight missions with reusable space technologies. Originally begun as the NASA X-37 project in 1999, the space plane was transferred to the U.S. Department of Defense in 2004. It had its first test flight on 7 April 2006. The space plane's first orbital mission, USA-212 was launched on 22 April 2010 using an Atlas V rocket. It returned to Earth on 3 December 2010 having successfully tested the vehicle's heat shield and hypersonic aerodynamic handling. A second X-37B was launched on 5 March 2011 with the mission designation USA-226.