On December 6, 1999, after a successful landing, a Global Hawk unmanned aerial vehicle (UAV) unexpectedly accelerated its taxiing speed to 178 mph and, at a curve in the runway, veered off the paved surface. Its nose gear collapsed in the adjacent desert, causing $5.3 million in damage. At the time of the accident, the operators piloting the UAV from the safety of their control station had no idea why it had occurred. An Air Force investigation attributed the acceleration to software problems compounded by “a breakdown in supervision.” A spokesperson for Northrop Grumman, the UAV’s manu...