In its continuing investigation of US Airways flight 1250 on March 22, 2008, in which a wing panel, measuring about 4 feet by 5 feet, separated from the B-757, the National Transportation Safety Board has developed the following factual information:
Although the separated wing panel has not been located, investigators have been able to examine the remaining components of the assembly to determine why the panel fastening system failed. Initial examination of these components revealed that two of the three clips that secured the leading edge of the panel to the wing had failed due to metal fatigue sometime prior to the incident flight. The remaining clip failed during flight 1250, causing the panel to separate from the aircraft.
After problems with the 757 wing panel fastening system were identified in the late 1980s, the Federal Aviation Administration issued an Airworthiness Directive (AD) requiring operators of 757s to install a redesigned fastening system. Eastern Airlines, which ceased operations in 1991, operated the 757 involved in this incident at the time the AD was issued in 1991, and had installed the redesigned system. It was these redesigned fasteners that failed on flight 1250.
Since the incident on March 22, US Airways reported to the Safety Board that it had inspected the wing panels on all of its 757s and found problems with wing panel fasteners on several other aircraft, which were since repaired and returned to service.
The Safety Board is continuing to evaluate the design, installation, inspection and maintenance of the failed components to determine the cause of the failure and the impact on the 757 fleet.
The NTSB has also reviewed the data extracted from aircraft's flight data recorder (FDR), and in conjunction with statements from the flight crew, the Safety Board found that there was no substantial change to the aircraft's handling characteristics after the panel separated from the wing. Because of this, the NTSB has reclassified this event from an accident to an incident.