SOUTHWEST

part of a wider investigation underway by the National Transportation Safety Board.

“I know it’s not ideal, but the NTSB owns the investigation and we are simply a party to it,” Landson said.

Investigators say a fan blade snapped off as Southwest Flight

1380 cruised at 500 mph high above Pennsylvania. The failure set off a catastrophic chain of events that killed a woman and broke a string of eight straight years without a fatal accident involving a U.S. airliner.

“This fan blade was broken right at the hub, and our preliminary examination of this was there is evidence of metal fatigue where the blade separated,” NTSB Chairman Robert Sumwalt said.

On Wednesday, federal investigators were still trying to determine howawindowcameoutofthe plane, killing a woman seated in that row. No plastic material from the window was found in the 737, Sumwalt told a news conference.

Family members have identified the woman as 43-year-old Jennifer Riordan, a banking executive and mother of two from Albuquerque, New Mexico.

Earlier incident

Metal fatigue — microscopic cracks that can splinter open under the kind of stress placed on jetliners and their engines — was blamed for an engine failure on a Southwest plane in Florida in 2016. Both that plane and the jet that made a harrowing emergency landing Tuesday in Philadelphia were powered by CFM56 engines.

Manufacturer CFM International, a joint venture of General Electric Co. and France’s Safran SA, recommended in June that airlines using certain CFM56 engines conduct ultrasonic inspections to look for cracks.

Last month, European regulators required airlines flying in Europe to conduct the inspections that were recommended by CFM.

In the U.S., the Federal Aviation Administration proposed a similar directive in August but has not yet required the inspections.

Too soon to tell

The Southwest CEO protested that it is too soon to say whether Tuesday’s incident is related to any other engine failures.

Kelly said Tuesday’s plane had flown 40,000 cycles. A cycle is one takeoff and one landing. Boeing delivered the plane to Southwest in July 2000, meaning that if the plane has been in continuous use it has made about three flights a day.

Kelly said the plane was inspected on Sunday and nothing appeared out of order.

There are several types of inspections that airline planes must go through, ranging from an “A check,” which is done about every eight to 10 weeks, to more-rigorous B, C and D checks.

A so-called D check is done roughly every six years for older planes, less frequently for newer ones. It can take weeks and involves taking apart much of the plane for inspection and possible repair or replacement of parts, then putting it back together. Engines are typically removed for work during a D check.

Southwest did not respond to requests to make maintenance records for Tuesday’s plane available, but NTSB investigators were heading to Dallas to inspect the records, Sumwalt said.