It is the stuff of movies, but on Tuesday, it became all too real for passengers on Southwest Airlines flight 1380, who said a woman was partially sucked out of the plane’s window after it was blown out when one of the aircraft’s engine exploded.

The woman, Jennifer Riordan of Albuquerque, was seated in Row 14, the same row as the missing window, federal investigators said Wednesday. Witnesses said passengers and flight attendants pulled her back.

The flight, which was headed to Dallas from New York’s La Guardia Airport, made an emergency landing at Philadelphia International Airport.

Riordan, a Wells Fargo Bank executive and mother of two, died later at a Philadelphia-area hospital. Seven other passengers were injured. Federal officials said Riordan’s death was the first passenger fatality on a U.S. carrier since 2009.

The Philadelphia Department of Public Health said Wednesday night that Riordan died of blunt-impact trauma to her head, neck and torso.

“The listed cause of death seems consistent with what we’ve heard in media reports,” department spokesman James Garrow said, though he could not confirm the nature of her death. “The cause that we’re listing and have written on the death certificate sounds consistent with what has been reported,” he said, but he could not say whether the injuries were caused by “the fuselage or the air or the window or debris.”

Robert Sumwalt, chairman of the National Transportation Safety Board, said investigators are aware of reports from passengers that Riordan was nearly sucked out of the plane, but that “we have not corroborated that ourselves.” He did say that there were no other holes in the cabin. Investigators also did not find any pieces of the window inside the plane.

The very idea that a passenger could be sucked out of an airplane midflight has rattled many travelers. Such incidents are rare but have happened. For example, in 1988, an Aloha Airlines flight attendant was pulled to her death after a hole opened in the roof during a flight to Honolulu from Hilo, Hawaii.

It’s all about air pressure, which varies depending on location. At sea level, atmospheric pressure is about 14.7 psi (pounds per square inch), Thomas Anthony, director of the University of Southern California’s aviation security program, told the Verge. But at an airplane’s cruising altitude, about 33,000 feet, it drops to about 4 psi. That is why the higher you go, the more difficult it is to breathe. The air gets thinner. It’s the reason climbers on Mount Everest must carry oxygen with them.

Aircraft cabins are pressurized to keep passengers comfortable and alive at high altitudes, said Jim Gregory, a professor of aeronautical engineering and director of the Aerospace Research Center at Ohio State University.

Without that pressurization, Gregory said: “Every passenger would suffer from hypoxia [a condition in which a person’s body doesn’t get enough oxygen] within a minute or less.”

Gregory said that the pressure level inside the Southwest cabin was probably about 11 psi, compared with 4 psi outside. While those numbers may not seem that far apart — the difference in pressure could be up to seven pounds per square inch. That could translate to roughly 600 pounds of force acting on each of the plane’s windows, which is why once the window was blown out, the resulting suction would be enough to pull a passenger from a seat.

“When the window ruptures, you have those two pressure levels trying to equalize,” said Ladd Sanger, an aviation attorney and licensed airplane and helicopter pilot. “The pressure inside the airplane is escaping out that hole to attempt to equalize, which is why it’s creating that suction and pulling from inside the aircraft.”

Those conditions explain how a passenger could be partially pulled into a small airplane window. And the difficulty of pulling them back in.

“You think about the pressure differential,” Sanger said. “It’s about somewhere between six and eight times.”

Gregory said while incidents like Tuesday’s are rare, they are an important reminder that travelers need to pay attention to the preflight safety briefings. That starts with the basics: wearing your seat belt and knowing how to properly wear the oxygen mask. Video from the Southwest flight showed people grabbing their masks and putting them over their mouths, but not their noses.

As the flight attendants always say during the safety briefings:

“In the event of a decompression, an oxygen mask will automatically appear in front of you. To start the flow of oxygen, pull the mask towards you. Place it firmly over your nose and mouth, secure the elastic band behind your head, and breathe normally. Although the bag does not inflate, oxygen is flowing to the mask. If you are traveling with a child or someone who requires assistance, secure your mask on first, and then assist the other person. Keep your mask on until a uniformed crew member advises you to remove it.”

Ashley Halsey contributed to this report.