I believe there was a trial set up when Lt Gen Israel USAF wanted to cut the U2 for the Global Hawk, the test was to photograph the Pacific Fleet then return to Beale. Part way through the trial the Nav systems and Comms Links were disabled. The pilot flew the U2 to Beale, the Global Hawk went to a pre programmed position where it would ditch. At least that was the story we were told in Cyprus, bottom line, the U2 is still operational 25 years later.