Northeast blackout of 2003

Power lines sagging into overgrown trees in Ohio started it, but software turned a local problem into a blackout affecting an estimated 55 million people across the north-eastern United States and Ontario on 14 August 2003. A race condition in the alarm system of FirstEnergy's GE XA/21 energy management software stalled it silently, so control room operators were unaware the alarms had failed for over an hour while lines tripped one after another. The lesson is about failing loudly. A monitoring system that stops without saying so is worse than none, because people keep trusting a quiet screen. Watch the watchers, and make the absence of updates an alarm in itself.