NEW YORK, United States (AFP) — US regulators on Tuesday ordered inspections of certain Pratt & Whitney airplane motors after an engine failure over the weekend that led to dozens of Boeing 777 aircraft being grounded worldwide.

"US operators of airplanes equipped with certain Pratt & Whitney PW4000 engines (must) inspect these engines before further flight," the Federal Aviation Administration (FAA) said.

The FAA said it was issuing the order "as a result of a fan-blade failure that occurred Saturday on a Boeing 777-200 that had just departed from Denver International Airport."

Metal fatigue has emerged as the chief suspect in the spectacular engine failure on a United Airlines plane, which scattered debris over suburban Denver.

The FAA said that "operators must conduct a thermal acoustic image (TAI) inspection of the large titanium fan blades located at the front of each engine. TAI technology can detect cracks on the interior surfaces of the hollow fan blades, or in areas that cannot be seen during a visual inspection."

Even prior to the Denver incident, US air safety regulators had been weighing stricter inspections on the jets and their Pratt & Whitney engines following a December 2020 incident in Japan, US officials said.

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.