From the placard:
The unmanned Boeing X-40A was the first-phase flight test vehicle for the US Air Force's Space Maneuver Vehicle (SMV) program that began in the late 1990s. The SMV program aimed at developing a new generation of small and reusable, highly maneuverable space vehicles for deploying satellites, surveillance, and logistics missions.
Designed and built by the Boeing Company in partnership with the Air Force Research Laboratory, the X-40A was produced at Boeing's Phantom Works facility at Seal Beach, California. This test aircraft was a 90 percent scale version of what would later be designated the X-37 space plane.
On August 11, 1998, the X-40A made its first successful flight at Holloman AFB, New Mexico. Lifted to an altitude of about 10,000 feet by a helicopter, the X-40A was released, and it made an unpowered flight to demonstrate high-speed guidance, navigation, and control capabilities.
Following that single flight, the USAF loaned the X-40 to the National Aeronautics and Space Administration (NASA) to test the shape, guidance, and other systems of the X-37. After captive-carry flights to practice release procedures and test equipment, the X-40A made its first flight for NASA on March 28, 2001. Carried aloft by a US Army helicopter to 15,000 feet before being released, the X-40A flew itself, guided by onboard systems, to a gentle landing at Edwards AFB, California. The X-40A made a total of seven successful flights in support of the X-37 program. This aircraft came to the Museum in 2008.