Southwest Airlines Co canceled more flights on Monday as it worked to complete inspections of engines like the one that failed last week in a deadly accident over Pennsylvania.

Flightaware.com, a website that tracks aviation cancellations, said Southwest canceled 129 flights on Monday, or 3 percent of its total flights, and delayed 468 other flights, or 11 percent. By contrast, other major U.S. carriers had each canceled four or fewer flights on Monday, the website said.

Southwest said the cancellations were the result of the company’s announcement last Tuesday that it would begin voluntarily stepping up inspections of some CFM56-7B engines over the next 30 days. The airline said on Sunday it canceled about 40 flights.

It said on Monday it anticipated “minimal delays or cancellations each day due to the inspections.”

The company added it “will continue our work to minimize flight disruptions by performing inspections overnight while aircraft are not flying, and utilizing spare aircraft, when available.”

The Federal Aviation Administration and European regulators ordered emergency inspections within 20 days of nearly 700 aircraft engines similar to the one involved in the fatalSouthwest engine blowout.

Southwest said the cancellations were not a result of the emergency directive.

The engine explosion on Southwest flight 1380 on Tuesday was caused by a fan blade that broke off, the FAA said. The blast shattered a window, killing a passenger, in the first U.S. airline passenger fatality since 2009.

Southwest has declined to answer questions about its CFM56-7B inspection program, including how many engines were inspected before the accident, and if the engine that failed had been inspected and if the new inspections turned up any problems.

The FAA said on Friday the “unsafe condition” was “likely to exist or develop in other products of the same type design.”

A Southwest flight in August 2016 made a safe emergency landing in Pensacola, Florida, after a fan blade separated from the same type of engine and debris ripped a hole above the left wing prompting two service bulletins from engine manufacturer CFM International, a joint venture co-owned by General Electric Co and France’s Safran SA.