Investigators have recommended Boeing strengthens an engine's “structural integrity” following a fatal accident.
A report by the US National Transportation Safety Board (NTSB) into the Southwest Airlines Flight 1380 accident in 2018, involving a Boeing 737 Next Generation (NG) aircraft, found a fan blade failed.
Passenger Jennifer Riordan died and eight others suffered minor injuries when the cabin depressurised during a flight between New York and Dallas.
Recommended changes to avaition safety procedures and the design of the Boeing 737 NG engine aim to prevent future vulnerabilities.
A fan blade in the left engine, which was weakened by fatigue cracks, detached and “impacted the engine fan case and fractured into multiple fragments”. The fragments hit the aircraft and damaged the window, leading to "rapid cabin depressurisation".
As a result of the investigation, the NTSB has recommended new safety procedures, including “ensuring the structural integrity” of the fan case on Boeing 737 NG aeroplanes, and assessment of other aeroplane designs and structures for similar risk of “critical fan blade impact locations”.
As well as ensuring flight attendants are secured in a jumpseat during emergency landings, guidance is available on how to safely reseat passengers when there are no seats in-flight, and improvements to inspections of fan blades to detect vulnerabilities such as fatigue cracks.
In response, aeroplane manufacturer Boeing has committed to working with the US Federal Aviation Administration (FAA), engine manufacturers, and industry stakeholders to make "design enhancements".
According to Boeing, this includes supporting engine manufacturers’ recommendations for fan blade inspections, enhancements being introduced into the inlet and fan case designs to improve their ability to withstand an engine fan blade fracturing, as well as to strengthen the overall structures.
A statement from Boeing on the NTSB Southwest 1380 recommendations said: “Safety and quality are Boeing’s top priorities and Boeing is committed to working closely with the FAA, engine manufacturers, and industry stakeholders to implement enhancements that address the NTSB’s safety recommendations.
“All 737 NGs are safe to continue operating normally as the issue is completely mitigated by the fan blade inspections... Once [design enhancements are] approved by the FAA, that design change will be implemented in the existing  NG fleet over the longer term. This issue is limited to the 737 NG and does not affect the 737 MAX.”