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When an engine of a Boeing 777 airplane exploded, sending parts tumbling to the ground in the suburbs of Denver, the news was familiar to investigators because this type of engine has been involved in multiple incidents. NPR's Russell Lewis reports.
RUSSELL LEWIS, BYLINE: The explosion happened four minutes after takeoff. Pilots heard a loud bang as parts of the Pratt & Whitney engine broke away, showering a suburb near Denver with debris. National Transportation Safety Board Chairman Robert Sumwalt says investigators located a broken fan blade in a field, and it had damage consistent with metal fatigue, tiny cracks from wear and tear.
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ROBERT SUMWALT: We can come up with a pretty accurate number of when that crack, that fatigue crack was initiated.
LEWIS: The incident is similar to one that happened in 2018 on another United 777 and a Japan Airlines jet last December, powered by the same Pratt & Whitney engines. Boeing asked airlines to stop flying 777s that use these particular engines until extra inspections can be completed. Eric Jones is a former 777 mechanic who chairs aviation maintenance at Embry Riddle Aeronautical University. He says there are many possible reasons for the failure.
ERIC JONES: It could be that somebody overlooked something during an inspection. It could be that something happened internally to that engine. It could be that it ingested something and caused damage maybe 25 flights ago.
LEWIS: The NTSB investigation is expected to take up to a year. Russell Lewis, NPR News. Transcript provided by NPR, Copyright NPR.
