Airlines around the world that operate planes with this engine type have already grounded affected jets. United, the only affected U.S. carrier, has voluntarily taken its 24 Boeing 777 airplanes with Pratt & Whitney engines out of service—a move that it said would affect its cargo shipments next month as it prepares to swap out parked planes to carry passengers.

United has additional impacted jets that were parked in storage and the carrier said Tuesday that it will comply with the FAA’s order to ensure that all the aircraft in its fleet meet its rigorous safety standards.

On Monday, U.S. safety investigators said they found evidence of “damage consistent with metal fatigue” on one of the engine’s fan blades that had been largely ripped off. That loose blade apparently then sheared off part of a second blade that was also fractured, according to

Robert Sumwalt,

chairman of the National Transportation Safety Board.

The FAA’s order, described as an interim measure, means it will be some time before planes with these engines can fly again. Boeing recommended airlines ground them and regulators in Japan ordered airlines there to stop flying them. In South Korea, regulators have only ordered special engine inspections, though

Korean Air

and

Asiana Airlines

have grounded all 777 jets with Pratt & Whitney powered engines that were in operation.

Typically, authorities in other countries issue orders based on the directive by the country that certified the aircraft or part, in this case, the U.S.

The FAA said it would review the results of thermal acoustic image inspections that can detect cracks on the interior surfaces of the fan blades that can’t otherwise be seen. Those results will determine how frequently such inspections will have to be performed going forward.

The incident over the weekend follows two similar engine failures involving the same type of engine on the same type of aircraft in recent years.

The FAA had previously mandated that this engine’s fan blades be inspected at regular intervals after a similar incident on a United flight in 2018.

The FAA had already been considering whether to order increased inspections of the Pratt & Whitney engines after another similar failure on a

Japan Airlines Co.

flight in December. Japan’s Transport Safety Board said a fan blade that had weakened over time broke off. Japan Airlines said it would inspect and replace those blades at more frequent intervals than what was called for previously in the FAA inspection regime.

In a statement, Pratt & Whitney said the engines will be shipped to one of its facilities for inspection to conform with the FAA action, which it said affected around 125 Boeing 777s. Boeing said in a statement that it supports the FAA’s guidance on inspection requirements.

—Doug Cameron and Eun-Young Jeong contributed to this article.

Write to Alison Sider at alison.sider@wsj.com