In 1994, American Eagle Flight 4184 encountered heavy air traffic and poor weather that postponed the arrival of this flight at Chicago's O'Hare International Airport, where it was to have landed en route from Indianapolis, Indiana. The ATR-72, a twin-engine turboprop carrying 68 people, entered a holding pattern southeast of O'Hare. As the plane circled, the freezing rain formed a ridge of glaze on the upper surface of its wings, eventually causing the aircraft's autopilot to suddenly disconnect and the pilots to lose control. The ATR disintegrated on impact with a field below. All passengers and crew were killed.