The Defense Department has conducted the first-ever autonomous midair refueling operation, a development that analysts say could unlock the potential of unmanned aircraft to conduct persistent missions lasting as long as 100 hours. In a little-noticed test conducted Aug. 30, an F/A-18 configured to operate as an unmanned test bed autonomously guided its fuel probe into the center of a 32-inch basket and fuel hose dangling in the turbulence of a modified 707-300 aerial refueling tanker flying over Edwards Air...