After an engine on a United 777 failed minutes after takeoff in Denver this past weekend, the Federal Aviation Administration (FAA) is ordering operators to conduct high-tech inspections of all Boeing 777s powered by the same Pratt and Whitney engine that failed "before further flight."
More than 100 Boeing 777s are either temporarily grounded, banned, or removed from service worldwide in response to the incident.
In the U.S., airlines like United will now be required to conduct a thermal acoustic image inspection of the engine's fan blades before the planes can return to the skies. This will allow inspectors to detect cracks on the inside of the large, hollow titanium blades that otherwise wouldn't be visible to the naked eye.
The agency is not increasing the frequency of these blade inspections yet, but the FAA said it will review the results on a rolling basis and it may revise the directive to set a new inspection interval.
"The FAA anticipates that further AD action will follow," the directive said.
During United Flight 328, one blade broke off mid-flight and struck another, causing significant damage to the front of the engine.
The National Transportation Board (NTSB) said Monday that the damaged blades showed signs of metal fatigue based on preliminary evidence. The NTSB has still not shared when this aircraft or engine was last inspected or how often it required inspection.
The FAA's order, called an "AD" or airworthiness directive, comes after multiple suspected similar failures. One occurred in 2018 when pieces of the same Pratt and Whitney series engine broke loose after a fan blade failure on a United 777. Another occurred in December 2020 when a fan blade broke in the same engine and debris hit the fuselage of a Japan Airlines 777.
Engine manufacturer Pratt & Whitney released a statement late Tuesday explaining that the process requires the fan blades to be shipped to Pratt and Whitney's FAA-authorized repair station for inspection so it can confirm their airworthiness.
The company added it is "coordinating all actions with Boeing, airline operators and regulators."
Boeing said it supported the FAA's guidance and "will work with [their] customers through the process."
United Airlines, the only U.S. carrier affected by the order, said it will comply with the AD to "ensure all all 52 of the impacted aircraft in our fleet meet our rigorous safety standards."
ABC News' Sam Sweeney, Jeffrey Cook, and Amanda Maile contributed to this report.
FAA orders inspections of some Boeing 777 engines after United failure
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