An aircraft that crashed in flames in Kentucky in November had a structural flaw that had been identified by Boeing on similar planes 15 years ago, according to investigators.
The MD-11F freighter operated by UPS crashed after one of its engines separated from the wing as it was preparing to take off from Louisville.
The plane briefly lifted off from the runway before hurtling out of control into an industrial area. Fifteen people died as a result, including three crew and 12 on the ground.
In an update report, the US National Transportation Safety Board (NTSB) revealed that cracks found in the engine mounting assembly had previously occurred on several other aircraft.
At the time, Boeing concluded that the issue would not result in a safety of flight condition.
The MD-11 is a relatively elderly design that was originally produced by McDonnell Douglas. Boeing acquired the company in 1997, with the last MD-11 coming off the production line in 2001. Boeing has continued to provide parts and service support.
In the aftermath of the Kentucky disaster, the NTSB's preliminary report highlighted cracks in the engine attachment mechanism. Its latest update describes fractures due to evidence of fatigue in a critical bearing and the mounting it is meant to sit in.
Boeing had previously identified failures of the same part on four occasions in different aircraft. In 2011, they sent a non legally-binding service letter to operators recommending inspections of the part every five years.
Tim Atkinson, a former air accident investigator, expressed concern about the NTSB report, stating, It's extraordinary that Boeing concluded that a failure of this part would not have safety consequences.
Criticisms have also been directed towards Boeing regarding other design flaws, specifically in its 737 Max model, which was implicated in two accidents leading to 346 deaths.
Boeing publicly stated they support the NTSB's investigation and offered condolences to those affected by the accident. The NTSB continues to investigate and has not yet drawn firm conclusions regarding the cause of the crash.
