The National Transportation Safety Board said on Sunday that an initial investigation showed that two fan blades in the plane’s Pratt Whitney PW4077 engine had fractured and that the cowling, or covering, had separated from the engine. Investigators are examining the engine and airplane as well as photographs and video taken by passengers. The cockpit voice recorder and flight data recorder were taken to Washington for analysis.
United said in a statement that “safety remains our highest priority — for our employees and our customers.” In addition to the two dozen planes it was grounding, United said it had 28 more Boeing 777s equipped with the engine model in storage.
While the American and Japanese orders affect relatively few planes, they represent yet another blow to Boeing, which is suffering from two recent major crises: the 18-month global ban of the 737 Max following two fatal crashes and a slowdown in worldwide travel caused by the coronavirus pandemic. The F.A.A. in November became the first global aviation authority to lift its ban on the Max, and its counterparts in several other jurisdictions have since followed suit.
The 777 is a large, twin-aisle plane typically used to fly long distances. Its first passenger flight, operated by United, was in 1995. So far, Boeing has delivered more than 1,600 of the jets to customers around the world, roughly 200 of which are freighters. Only 174 of the 1,600 jets were equipped with Pratt Whitney engines, the last of which was delivered to the South Korean carrier Asiana Airlines in 2013. More than 1,250 of the jets were equipped with engines made by GE Aviation, with the remaining using engines made by Rolls-Royce.
In recent years, airlines have increasingly favored smaller, single-aisle planes, a trend accelerated by the pandemic, throughout which few people have been flying internationally.
The Sunday F.A.A. order came hours after Japan’s aviation authority told All Nippon Airways and Japan Airlines to stop using 777s equipped with the Pratt Whitney engine.
“We have ordered that operation of the planes be stopped while we consider the necessity of additional measures,” the Japanese Ministry of Land, Infrastructure Transport and Tourism wrote in an announcement on its website.