The National Transportation Safety Board focused on why government regulators and the aviation industry failed to recognize a troubling pattern of defects before a UPS cargo plane crash killed 15 people in Louisville, Kentucky, last November. After the plane’s engine separated from the left wing during takeoff at Muhammad Ali International Airport, investigators discovered cracks in critical engine mount components.
Further examination revealed that similar flaws had been identified on 10 other aircraft over the previous 15 years. However, only four of those cases were reported to the Federal Aviation Administration. Investigators said all of them should have been reported because the missing information prevented regulators from identifying a broader safety trend.
The crash involved an MD-11 cargo aircraft. The engine detached as the aircraft accelerated down the runway, leading to a crash that killed all three crew members and 12 people on the ground. Another 23 people were injured. According to investigators, there has been only one other crash involving a similar aircraft model in which an engine separated from the wing.
Families of the victims argue that warning signs existed for years and that earlier action could have prevented the tragedy. Attorney Bradley Cosgrove described the disaster as a systemic failure to recognize and address a known risk before it resulted in catastrophe.
Maintenance Concerns and Prior Defects
During hearings, UPS officials testified that information provided over the years did not adequately communicate the seriousness of the problem. David Springer, who oversees aircraft maintenance and repair for UPS, said Boeing service letters described the spherical bearing issue in a way that appeared relatively minor and did not explain the potential damage to engine attachment points.
Investigators found that the critical components had not received a detailed inspection since October 2021. Another major inspection was not scheduled for approximately 7,000 more takeoffs and landings. After the Louisville crash, all MD-11 and DC-10 aircraft were grounded for inspections, and similar defects were discovered on three additional UPS aircraft and one DC-10.
The FAA testified that the limited number of reports it received was insufficient to demonstrate a significant safety trend. Boeing had previously concluded that the defects would not create a direct flight safety issue and therefore recommended additional inspections without requiring repairs or changing maintenance schedules. Because no formal FAA airworthiness directive was issued, airlines were left to determine whether additional maintenance was necessary.
Historical Warnings and Industry Response
Investigators noted similarities to the 1979 crash of a DC-10 in Chicago that killed 273 people after an engine detached from the aircraft. Although that accident was ultimately attributed to maintenance damage caused during engine installation, concerns about the same spherical bearing design were raised by manufacturer McDonnell Douglas, which later merged with Boeing.
FAA official Melanie Violette said the industry misunderstood the risks associated with bearing failures. Engineers believed the design was fail-safe because one side of the attachment structure could continue carrying the load if the other side failed. In practice, however, the failures occurred differently than expected.
Following the Louisville disaster, Boeing conducted extensive engineering studies to better understand stresses on the affected components and reviewed other aircraft designs for similar vulnerabilities. UPS officials acknowledged that stronger action might have been taken had they fully understood the potential consequences.
MD-11 Aircraft Return to Service
Despite concerns that MD-11 aircraft might never return to service, Boeing and the FAA developed a corrective plan that allows continued operation. The solution focuses on more frequent inspections and mandatory replacement of spherical bearings.
Under the updated maintenance requirements, bearings must now be replaced after every 4,000 takeoff-and-landing cycles. This approach was approved by the FAA as a way to address the safety concerns without requiring extensive redesigns.
While some operators have resumed flying the aircraft, UPS has announced plans to retire its MD-11 fleet. Meanwhile, FedEx resumed MD-11 cargo operations on May 10. Another operator, Western Global Airlines, has not yet announced its long-term plans for the aircraft type.
The NTSB’s final report is expected more than a year after the crash and will examine all contributing factors before determining the official cause of the disaster.
