This New Scientist article, about the Global Hawk unmanned aircraft receiving permission to routinely fly in civilian airspace, is pretty, well, routine until you get to the "accident report":

The USAF has only ever lost three Global Hawks, says Northrop Grumman. The first was during the plane's development, when someone accidentally tested the self-destruct program. As a result the plane flew to a pre-programmed, remote location and nose-dived into ground as its operators looked on helplessly.

I don't know... I just keep getting an image of Ren and Stimpy flying this thing, with Ren telling Stimpy, "You EEEdiot... don' push dis button, ever EVER EVER!"