Jeremiah Cornelius writes: According to Associate Press, the Air Force announced the failure of the X-51A Waverider, after being dropped by a B-52 bomber off the California coast. The unmanned experimental aircraft was designed to reach Mach 6, or 3,600 mph. suffered a control failure during an attempt to fly at six times the speed of sound. But the Air Force said that a faulty control fin prevented it from starting its exotic scramjet engine and the craft was lost. The first Boeing-designed X-51A achieved Mach 5 for about 140 seconds in 2010. A second Waverider flight last year ended prematurely with the craft trying to restart its engine until it plunged into the Pacific.