TWA Flight 529 was a Lockheed Constellation L-049 propliner, registration N86511, operating as a scheduled passenger service from Boston, Massachusetts to San Francisco, California. On September 1, 1961, at 2:05 a.m. local time, the flight crashed shortly after takeoff from Midway Airport in Chicago, killing all 73 passengers and 5 crew on board. At the time it was the deadliest single plane disaster in U.S. history.
The four-engine propliner originated in Boston, and after making intermediate stops in New York and Pittsburgh, arrived at Chicago Midway Airport at 1:18 a.m. CST where a new crew took over, and fuel and oil were added. At 2:00 a.m. the flight departed from runway 22, bound for Las Vegas, Nevada, the next stop. Five minutes later, while climbing westbound to 5,000 ft, the aircraft suddenly pitched violently upwards, resulting in an accelerated stall from which the crew was unable to recover. The aircraft crashed into a cornfield, and left a debris field of 200 by 1,100 feet.
The accident was investigated by the Civil Aeronautics Board, which concluded its probable cause was the loss of a 5/16 inch bolt which fell out of the elevator control mechanism during the climb from Chicago, resulting in an abrupt pitch up followed by a stall and crash.