The Federal Aviation Administration (FAA) has ordered emergency inspections of jet engines like the one in this week's fatal Southwest Airlines accident. The agency said its order affects 352 engines in the U.S. and another 681 worldwide on "new generation" Boeing 737 jets. Each aircraft has two engines.

Operators will have 20 days to inspect 737's with engines that have had approximately 30,000 takeoffs and landings.

The requirement from the agency comes after the engine maker, CFM International, issued a service bulletin recommending that more engines be inspected. At issue are the engine fan blades on Boeing 737-600, 700, 800 and 900 jets.

Get Breaking News Delivered to Your Inbox

The National Transportation Safety Board (NTSB) believes one of the blades snapped on the Southwest flight Tuesday, hurling debris that broke a window and led to the death of a passenger who was sucked part way out of the plane. The jet, which was headed from New York to Dallas, made an emergency landing in Philadelphia.

NTSB thanks the community for continuing to provide pieces of the engine cowling from @SouthwestAir #flight1380. Anyone

who has found additional pieces please contact witness@ntsb.gov pic.twitter.com/Eon8Vh6pCf — NTSB_Newsroom (@NTSB_Newsroom) April 20, 2018

The CFM 56-7B engines are on about 1,800 "new generation" 737s in service in the U.S. and about 6,400 worldwide.

Moments after the 737's engine exploded, Southwest passengers rushed to help those injured.

"I'm very proud of him. This is a calling that he has and he did amazing," said Stephanie Needum, who was on board Flight 1380. Her husband Andrew, a firefighter from Texas, knew something was wrong and it was happening seven rows behind him.

"I looked at her eyes and she basically gave me the approval to go back there. I felt moved to act, as well as other people on that plane. Tim McGinty, he was my big guy. Had my back," Andrew Needum said.