United airlines said Sunday it is “voluntarily and temporarily” halting flights of Boeing 777s with Pratt & Whitney 4000 engines of the sort that disintegrated shortly after takeoff Saturday on a United flight out of Denver.

The airline said the grounding affects 24 jets that were in active use. Its fleet of 777s also includes 28 that are currently in storage.

“Since yesterday, we’ve been in touch with regulators at the NTSB and FAA and will continue to work closely with them to determine any additional steps that are needed to ensure these aircraft meet our rigorous safety standards and can return to service,” the airline said in a statement. “As we swap out aircraft, we expect only a small number of customers to be inconvenienced.”

United continued: “Safety remains our highest priority — for our employees and our customers. That’s why our pilots and flight attendants take part in extensive training to prepare and manage incidents like United flight 328. And we remain proud of their professionalism and steadfast dedication to safety in our day to day operations and when emergencies like this occur.”

News reports out of Japan on Sunday said that nation’s regulators had grounded the 32 Boeing 777s flown by its two leading airlines.