Kingda Ka
In the past, Kingda Ka has been struck by lightning and shut down for almost a whole year. The launch cable snapped once and the ride was shut down for a while. Something happened to the braking fins so they shut down the ride. It also can get shut down by weather. The train is made so that if it rolls back it gets placed back to be launched. This happens when the hydraulic launch system does not get enough power to get over the hill or the brakes on the top off the hill stop you too much.