Background
On the day of the accident, TWA Flight 529 was preparing for departure from Midway Airport. During engine runup, the flight received its air traffic control clearance: "cleared to the Las Vegas Airport via Victor 6 Naperville, Victor 8 flight plan route, maintain 5,000 feet." The clearance was acknowledged correctly, and Flight 529 departed on runway 22L at 0200, making a right turn out of traffic.
Weather Conditions
The 0200 Midway Airport weather reported scattered clouds at 10,000 feet, high overcast, visibility three miles in haze and smoke, and wind south at eight knots. The Chicago O'Hare Airport weather at 0200 indicated partial obscuration, scattered clouds at 15,000 feet, high overcast, visibility two and one-half miles in ground fog and smoke, and wind south at six knots.
Accident Sequence
Radar contact was established with Flight 529 one minute and 34 seconds after takeoff clearance acknowledgment, as the aircraft proceeded outbound in a right turn. At 0204, the departure controller observed Flight 529 on radar five miles west of Midway Airport proceeding on course. Simultaneously, Northwest Airlines Flight 105 was cleared for takeoff on runway 22L at Midway and took off immediately. The ground controller observed a flash west of Midway Airport and asked Flight 105 if they had seen it. Flight 105 confirmed seeing a flash fire and stated they would fly over the area. As Flight 105 reported over the fire, radar range was noted to be nine miles west of Midway Airport, and the radar return of TWA Flight 529 had disappeared from the scope. It was later determined that Flight 529 had crashed at this site and the observed ground fire was the result of the accident. The airplane disintegrated in a field, and all 78 occupants were killed.
Probable Cause
The official investigation determined the probable cause of this accident to be the loss of an AN-175-21 nickel steel bolt from the parallelogram linkage of the elevator boost system, resulting in loss of control of the aircraft.