NEW YORK, United States (AFP) — US regulators had been weighing stricter engine inspections prior to last week’s fiery engine failure on a United Airlines plane over Denver, the Federal Aviation Administration said Tuesday.

The FAA reviewed inspection records and maintenance history after a Japan Airlines fan blade incident on December 4, 2020 “to determine the cause of the fracture and was evaluating whether to adjust blade inspections,” an FAA spokesman said Tuesday. The Japan flight landed without injury.

On Saturday, a United Airlines Boeing 777 plane quickly returned to Denver after liftoff due to engine failure. No one was injured in the Denver incident.

Both the Denver flight and the Japan Airlines plane involved seasoned Boeing 777 planes with the same kind of Pratt & Whitney engine.

That kind of engine was also used in a February 2018 United Airlines flight that also suffered engine failure before being safely landed.

The FAA reviewed 9,000 fan blade inspection reports and issued an airworthiness directive setting new rules on inspections following the February 2018 incident, the FAA spokesman said.

On Monday night, the National Transportation Safety Board said a preliminary review of the damage suggested the Denver incident was caused by “metal fatigue,” which is typically visible in marks left on the material.