The Federal Aviation Administration on Friday ordered ultrasound inspections of hundreds of jet engines like the one that blew apart at 32,000 feet in a deadly accident aboard a Southwest Airlines plane.

The agency said the order affects 352 engines in the U.S. on new-generation twin-engine Boeing 737s, a workhorse jet widely used by airlines around the world.

The National Transportation Safety Board believes one of the engine fan blades snapped on the Southwest flight Tuesday, hurling debris that broke a window and led to the death of a passenger who was sucked partway out of the 737. The jet, which was headed from New York to Dallas with 149 people aboard, made an emergency landing in Philadelphia. NTBS investigators said the fan blade that broke off was showing signs of metal fatigue – cracks from repeated use that are too small to be seen by the naked eye.

Engine maker CFM International issued a service bulletin earlier in the day.