Braniff Airways Flight 542

Braniff Airways Flight 542 was a scheduled flight between Houston International Airport and Idlewild Airport in New York City. On September 29, 1959, while flying to a scheduled stop at Dallas Love Field, the Lockheed L-188 Electra performing the flight broke apart in mid-air, approximately 3.8 miles (6.1 km) southeast of Buffalo, Texas, killing everyone on board. The flight up to that point had been uneventful. Eyewitnesses saw and heard a loud explosion in the air and the aircraft plummeted to the ground. The left wing landed more than a mile (2 km) from the rest of the wreckage, and had broken off the airplane near the fuselage.

The aircraft involved had been used in commercial service for only nine days since its delivery from the factory. Investigators combed through the wreckage in search of a cause of the breakup, but after six months, they still had not been able to find the cause. As they were preparing to close the investigation, Northwest Airlines Flight 710 crashed near Cannelton, Indiana on March 17, 1960. That aircraft was a seven-month-old Lockheed Electra, and witnesses to that accident described seeing the aircraft explode in flight, then crash to the ground. Investigators found that the entire right wing and portions of the left wing had broken off the aircraft while it was in flight.

The similarities between the two crashes led to the Federal Aviation Agency placing flight restrictions on the relatively new Lockheed Electra until a cause of the crashes could be identified, and ordered Lockheed Corporation to reevaluate the structural integrity of the aircraft and demonstrate its airworthiness. The subsequent investigation, involving over 250 engineers and technicans, discovered that when an Electra with damage to the mounting structures of one of the outboard engines flew at high speeds or in areas of turbulence, a destructive phenomenon called whirl mode wing flutter could occur, leading to wing failure. After discovering what had caused the crashes, Lockheed launched a program to design the needed structural changes to the aircraft to prevent whirl mode wing flutter from occurring and to apply retroactive modifications to all Electras that were already in service. The changes were successful in resolving the issue, and modifications to the final aircraft were completed on July 5, 1961.