SEATTLE: 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.

Even prior to the Denver incident, the United States 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 on Tuesday (Wednesday in Manila).