The Federal Aviation Administration said late Tuesday that Pratt & Whitney engines on Boeing 777 planes must be inspected before the jets can fly again in the United States.
On Saturday, one of the engines caught fire during a United Airlines flight and showered debris over Colorado, the latest such episode involving that engine family in recent years.
United is the only American airline that operates Boeing 777s equipped with the PW4000 engine series, and the airline said on Sunday that it was grounding those 24 planes in its active fleet while it awaited F.A.A. guidance. In December, a similar Pratt & Whitney engine failed aboard a 777 operated by Japan Airlines.
United said it would ensure that those two dozen planes and 28 more in storage comply with the F.A.A.’s order. Pratt & Whitney said in a statement that the safe operation of the fleet was its “top priority.”
Before the jets can fly again, the large, titanium hollow fan blades at the front of each engine must be removed and shipped to a Pratt & Whitney facility where they will undergo a “thermal acoustic image” inspection, according to the F.A.A. Under that technique, a fan blade is bombarded with high-frequency vibrations, raising its temperature. A thermal image of the blade is then recorded and analyzed for unusual readings that may signify a potential crack.
In 2018, a United flight involving the same plane-and-engine combination suffered a similar failure, prompting the F.A.A. to order engine inspections every 6,500 flights. In its statement on Tuesday, the agency said it might still adjust that inspection frequency.
Also on Saturday, a Boeing 747 equipped with a relative of that engine suffered a similar fate, shedding parts in the Netherlands. Europe’s aviation authority has said it does not believe that episode is related to the other failures. None of the four engine failures resulted in deaths. Two people were reported to have suffered minor injuries in the Netherlands.