Associated Press

Boeing has recommended that airlines ground all 777s with the type of engine that blew apart after takeoff from Denver this weekend, and most carriers that fly those planes said they would temporarily pull them from service.

The U.S. Federal Aviation Administration ordered United Airlines to step up inspections of the aircraft after one of its flights made an emergency landing at Denver International Airport Saturday as pieces of the casing of the engine, a Pratt & Whitney PW4000, rained down on suburban neighborhoods.

None of the 231 passengers or 10 crew were hurt, and the flight landed safely, authorities said. United is among the carriers that has grounded the planes.

FAA Administrator Steve Dickson identified the focus on the stepped-up inspections as hollow fan blades unique to the Pratt & Whitney PW4000 engine model and used solely on Boeing 777s. Dickson’s statement said the conclusion was based on an initial review of safety data and would likely mean grounding some planes.

Robert Sumwalt, chairman of the National Transportation Safety Board, said during a virtual news conference Monday night that a fractured fan blade found in the engine had visible signs of “damage consistent with metal fatigue.” The broken blade hit and fractured the blade next to it as the engine broke apart, according to a preliminary investigation.

Sumwalt said the blade that fractured first was being flown on a private jet to Pratt & Whitney’s headquarters Monday night to be examined under the supervision of NTSB investigators.

“Our mission is to understand not only what happened, but why it happened, so that we can keep it from happening again,” he said.

Boeing said there were 69 777s with the Pratt & Whitney 4000-112 engines in service and another 59 in storage and affirmed they should be grounded until the FAA sets up an inspection regime.

United had 24 of the planes in service; it is the only U.S. airline with the engine in its fleet, according to the FAA.

“We are working with these regulators as they take actions while these planes are on the ground and further inspections are conducted by Pratt & Whitney,” Boeing said in a statement, referring to American and Japanese regulators.

The engine maker said it was sending a team to work with investigators.

The emergency landing this past weekend is the latest trouble for Boeing, which saw its 737 Max planes grounded for more than a year after two deadly crashes in 2019 and is suffering amid the huge reduction in air travel due to the coronavirus pandemic. The Max planes began returning to the skies late last year — a huge boost for the aircraft maker, which lost billions during the grounding because it has been unable to deliver new planes to customers.

A Boeing 747 jet engine exploded in midair Saturday over the Netherlands, dropping metal debris that injured two people, according to Dutch authorities.

The plane, a cargo jet operated by charter company Longtail Aviation, began experiencing engine problems shortly after it took off from the town of Maastricht in the Netherlands, bound for New York City, CNN reported.

Witnesses heard explosions, and air traffic control informed the pilot that one of the plane’s engines was on fire, according to Reuters. The plane scattered parts over the Dutch town of Meerssen, injuring two people and damaging property.

The plane made an emergency landing at Liege Airport, in Belgium.