There were no injuries on the plane or on the ground. AFP/Michael Ciaglo/Getty Images
NEW YORK - Metal fatigue has emerged as the chief suspect in last week's spectacular engine failure on a United Airlines plane, which scattered debris over suburban Denver and led to dozens of Boeing 777 aircraft being grounded worldwide.
The incident on the Hawaii-bound flight -- which quickly returned to the airport after part of the engine caught fire and broke off -- prompted United and other airlines to ground planes with the same Pratt & Whitney engine.
While no one was injured in the Denver incident, the episode is the latest setback for Boeing, which only recently resumed deliveries of the long-grounded 737 MAX following two fatal crashes of that plane.
"A preliminary on-scene exam indicates damage consistent with metal fatigue," Robert Sumwalt, chair of the US National Transportation and Safety Board (NTSB), told a briefing.
He said two fan blades fractured on the number 2 engine on the Boeing 777-200. One of them was later found on a soccer field, while the other remained lodged in the engine.
Boeing said all 128 of the 777s with Pratt & Whitney engines were grounded following Saturday's emergency landing of United flight 328.
Of the 128 planes, only 69 were in service while 59 were in storage.
Besides United, which removed 24 planes from service, affected airlines included Japanese carriers Japan Airlines and All Nippon, and South Korea's Asiana and Korean Air.
Aviation experts said the incident especially raised questions about Pratt & Whitney and United over engine maintenance.
"It's nothing like the MAX," said Teal Group aviation analyst Richard Aboulafia. "After all these years of service it is unlikely to be a design issue with the engine, certainly it is something to do with maintenance."
The Denver incident followed a Japan Airlines 777 incident in December involving the same type of engine, as well as an engine problem in February 2018 on a United flight.
"There might be a common theme" among the three incidents "but until the investigation is complete, we don't know that," said Scott Hamilton of Leeham News, an aviation news site.