Swissair Flight 111 (1998)
A simple failure in the electrical system of The McDonnell Douglas MD-11 crash prompted changes in future aircraft’s electrical systems to prevent horrible results such as this one. During the flight, “inside the attic, a high-power wire supplying the new in-flight entertainment system suffered a failure that led to electrical arcing.” The fire spread exponentially throughout the plane, with no chance of stopping it, causing fatalities of everyone on board (Medium).