Some planes grounded after engine blows apart

DENVER— The Federal Aviation Administration has ordered airlines in the United States to ground planes with the type of engine that blew apart after takeoff from Denver this past weekend until they can be inspected for stress cracks.

The FAA’s order issued late Tuesday applies to U.S. operators of airplanes equipped with certain Pratt & Whitney PW4000 engines, which are used solely on Boeing 777s. Before the planes can fly again, operators must conduct a thermal acoustic image inspection of the large titanium fan blades at the front of each engine.

The FAA directive is a blow to United Airlines, which had 24 of the planes in service and is the only U.S. airline with the engine in its fleet.

A United flight from Denver to Honolulu made an emergency landing shortly after takeoff Saturday as pieces of the engine’s casing rained on suburban neighborhoods. 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 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.

The FAA directive said the agency would review the results of the inspections “on a rolling basis.”