A New X Plane:

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.