Chicago (CBS) – The investigation continues as to what caused the engine to explode on a Southwest Airlines jet yesterday that killed one passenger.

Jennifer Riordan, a married mother of two, died yesterday when engine parts shattered a window on Flight 1380 from New York to Dallas. Riordan was partially sucked out of the shattered window, while other passengers pulled her back into the plane and tried unsuccessfully to perform CPR.

Roughly 20 minutes after takeoff at around 32,000 feet in the air, the Southwest flight’s left engine exploded, sending shrapnel tearing through one of the plane’s windows, causing the cabin to lose pressure.

“I thought I was cataloguing the last moments of my existence. It felt like it was free-falling,” recalls Marty Martinez, one of the passengers on board, as he reached for oxygen masks as the plane descended rapidly.

Passengers are calling the female pilot, Captain Tammie Jo Shults, a hero for calmly guiding the plane to safety.

Captain Shults is a former fighter jet pilot. According to her friends at her alma mater, Shults was among the first female fighter pilots in the U.S. Navy.

“The fan section that we are talking about today is designed such that if a part does come off, it would not be catastrophic for the airplane. Had this window not been punctured, today’s event would just have been another emergency landing,” explains NTSB Chairman Robert Sumwalt

Tuesday’s engine failure isn’t the first emergency landing for Southwest linked to metal fatigue. In August 2016, a similar event occurred on a flight to Orlando. That flight landed safely and no one was hurt, but metal from the engine sliced into the fuselage.

“We are very concerned about it,” says Sumwalt. “There needs to be proper inspection mechanisms in place to check for this before there’s a catastrophic event.”