The Air Force has designated the Air Force Research Lab’s Active Aeroelastic Wing flight demonstrator the X-53. An AFRL release notes that this is the first X-plane initiated within the Air Vehicles Directorate since the X-24 lifting body concept. The AAW flight demonstrator, a joint project of AFRL, NASA, and Boeing, is an F/A-18 highly modified to exploit aeroelastic effects normally considered anathema to aircraft performance. AFRL officials say the X-plane designation lends the program more import.
Air Force depots are not typically meant for quick repair jobs, but during Operation Epic Fury, the service moved some of its stateside heavy maintenance capability forward to fix battle-damaged aircraft closer to the fight.
