A passenger on Southwest Flight 1380 described the sudden noise when the engine blew as like "a marble hitting glass."

Then, a roar as the plane depressurized.

Flight attendants trying to ensure passengers were receiving air through emergency masks that dropped from the ceiling recalled the noise, coupled with the sudden pressure drop's effect on their ears, leaving them nearly deafened.

"Because of the pressure in her ears, she could barely hear anything," according to documents federal safety officials released Wednesday, describing the experience of flight attendant Rachel Fernheimer that morning over Pennsylvania, April 17, 2018. "The cabin was loud and windy."

Fernheimer tried to remember her training and walked along the aisle, holding hands, telling passengers they would be OK, saying the plane would land. She couldn't know that, though. Over the noise, she couldn't hear anything from the flight crew. She checked on passengers' oxygen masks, some of which had air hoses that had come loose. She reconnected those tubes to the oxygen supply, and showed other passengers how to wear the masks properly.

When she reached Row 14 of the two-engine jet, a horrifying sight greeted her. The head, torso, and arms of the woman in Seat 14A had been sucked through a 10.5- by 14.37-inch window. Another flight attendant, Seanique Mallory, was pulling on the woman's body. Fernheimer got on the floor and grabbed one of the woman's legs.

The window damaged in the engine failure on Southwest flight 1380.
National Transportation Safety Board
The window damaged in the engine failure on Southwest flight 1380.

As they struggled to keep Jennifer Riordan, 43, inside the plane, a passenger reached out of the window and grasped the woman's shoulder. The pressure had begun to equalize, and the passenger pulled in her arm, then her head. Injuries to the New Mexico mother of two would prove fatal.

New details about the Boeing 737-700 that lost an engine about 50 miles from Philadelphia emerged from a trove of documents released by the National Transportation Safety Board before a 9 a.m. hearing Wednesday in Washington.

The jet carried 144 passengers and five crew. Its left engine blew after a fan blade broke while spinning at 5,149 rotations per minute and shredded the engine and its casing. Pilot Tammie Jo Shults — one of the first female fighter pilots in the Navy — was able to land the aircraft, which had taken off from New York City's LaGuardia Airport and was headed to Love Field in Dallas, about 20 minutes later at Philadelphia International Airport, with all those on board except Riordan surviving with minimal injuries.

At the first half of the NTSB hearing Wednesday morning, questions focused on the testing that titanium fan blades undergo and the engine casing's ability to contain a catastrophic event. The NTSB documents note that for pieces of the inlet, which directs air into the engine, and cowling to break free due to the fan blade failure was unexpected, as was the damage to the window. The safety agency took testimony from officials from Southwest, Boeing, the Federal Aviation Administration, and CFM International, the engine's manufacturer. Southwest officials stated during the hearing that the CFM56-7 engine on Flight 1380 did not need to undergo intensive testing under the standards at the time of the incident.

Tammie Jo Shults in the early 1990s.
Linda Maloney
Tammie Jo Shults in the early 1990s.

Fan blades experience enormous strain during a flight, drawing thousands of pounds of air into the engine. The amount of use a fan blade can have without inspection has been halved since the Philadelphia incident, but during Wednesday's hearing, Bella Dinh-Zarr, a member of the NTSB board, asked whether fan blades should have a mandated age at which they are pulled from use.

It was something that officials were looking into, said Christopher Spinney, who testified for the FAA. Eight blades have been pulled from service due to the discovery of cracks since the Philadelphia incident, the NTSB reported at the hearing.

Also under investigation is why the inlet and the cowl that surrounds the engine didn't contain the damaged engine, and didn't prevent debris from spraying forward into the fuselage. A virtually identical fan-blade failure occurred on another Southwest flight, over Pensacola, Fla., in 2016, but no one was injured. Investigators are looking at whether the angle of impact of the fan blade on the casing was the reason the Philadelphia incident turned deadly, and whether further testing and precautions are needed to secure the parts surrounding an engine.

In a statement Wednesday, CFM International noted it had moved aggressively to address the concerns raised by the accident.

"All of the CFM56-7B fan blades targeted by the various Airworthiness Directives were cleared by mid-August 2018, ahead of the August 31 deadline," wrote the company, a cooperative between the French company Safran Aircraft Engines and General Electric.

Pieces of the plane rained down on Berks County, some of them small fragments of metal, others large sheets torn from the ruined engine. All the recovered parts landed in Bernville, a community of about 1,000 people.

A piece of blue metal, later determined to be a section of the inboard fan cowl, landed on the women's tee of the 17th hole at the Heidelberg Country Club. Part of the fan-cowl frame was found in the tree line that separates the 9th and 16th fairways. A section of the outer engine barrel plummeted onto state land, where it was found by two Pennsylvania Game Commission employees. Investigators found debris up to 65 miles away from Philadelphia.

pieces of the engine casing found from Southwest flight 1380.
National Transportation Safety Board
pieces of the engine casing found from Southwest flight 1380.

Riordan's cabin window shattered fewer than 3.2 seconds after the engine failure, according to the NTSB documents. Within five seconds, the passenger cabin had depressurized. After Fernheimer helped pulled her back into the plane, the flight attendant caught a glance of the ruined engine. Blood covered the passenger windows outside.

The people helping Riordan laid her across the row of seats once they pulled her back in. One passenger, a registered nurse, came to assist. Another, a  paramedic, began to perform CPR.

Passengers kept asking: Would they make it? The captain's voice came over the speakers, calm, announcing they would be landing in Philadelphia.

We're going to make it, Fernheimer insisted.

She moved forward to check on more passengers. When she left Riordan's row, the paramedic and nurse were still performing chest compressions on the woman. The Philadelphia medical examiner would eventually find that her spine had been broken in two places. She also suffered terrible head injuries, internal bleeding, multiple fractured ribs, and many cuts and scrapes of her face, neck, chest, back and arms. The cause of death was "blunt trauma of the head, neck and torso."

While passengers and flight attendants fought to save Riordan, the plane's captain and first officer were facing chaos and shock. In the cockpit, Shults described losing a sense of time amid the chaos. She struggled with the plane's suddenly sluggish controls, she told investigators, and she and her first officer, Darren Lee Ellisor, experienced seven to 10 minutes when they couldn't communicate with anyone else on the plane.

The Southwest Airlines jet shown inside a hangar at Philadelphia International Airport the day after the incident.
Tim Tai / Staff Photographer
The Southwest Airlines jet shown inside a hangar at Philadelphia International Airport the day after the incident.

Ellisor, 44, was flying the craft at about 32,000 feet when the engine exploded. He heard a loud bang, and almost immediately felt extreme vibration as the plane veered hard to the left.

Fog and dust filled the cockpit. Horns sounded. The sudden decompression took Ellisor's breath away. He told investigators it was the "most memorable few seconds" of his aviation career.

Unable to hear the captain or air traffic control, he disconnected the autopilot and automatic throttle, donned his oxygen mask, and began taking the plane down, only to realize it was already beginning to descend on its own.

Within two minutes of the explosion, at 25,000 feet, Shults, 56, took control of the aircraft. Ellisor turned his attention to a checklist to determine what had happened to the plane. The fog in the cockpit led the crew to think there was a fire, but its sensors did not detect a blaze.

Shults told her first officer the flight controls were dragging and that the plane's hydraulic system must have been damaged. Throughout, Shults kept thinking of the No. 1 directive in Southwest's emergency procedures: "Maintain aircraft control."

The suggestion from air traffic control was that she land at Harrisburg International Airport in Middletown, Pa. But the captain requested Philadelphia. Shults initially wanted the 20-mile final approach to give her and Ellisor time to work through their checklists. But news about the gravely injured passenger changed her mind. The goal now was to get on the ground as fast as possible.

Ellisor described the landing on Philadelphia's Runway 27 as "great." Fire trucks greeted the plane. After several frustrating attempts to talk to rescue teams over radio, he eventually yelled to the fire chief out the plane's forward door.

From Wednesday’s NTSB hearing into the April 17, 2018 Southwest Airlines engine failure over Berks County.
NATIONAL TRANSPORTATION SAFETY BOARD
From Wednesday’s NTSB hearing into the April 17, 2018 Southwest Airlines engine failure over Berks County.

Staff writer Dylan Purcell contributed to this article.