Brittany Oswell suddenly felt ill about three hours into her flight from Hawaii to Texas. She was dizzy, disoriented and slurring her speech. Then she briefly fainted.

A flight attendant on the American Airlines flight in April 2016 tracked down a doctor on board who examined her. She may have had a panic attack, the doctor said. But it soon became clear her condition was far worse.

About an hour later, Oswell, 25, collapsed in a lavatory, defecated and vomited on herself, and threw up on flight attendants who had come to check on her. The doctor returned and this time issued an urgent request to the flight crew: The pilot must land the plane immediately.

The frenzied efforts by her husband and the doctor to save Oswell, who died three days later in a hospital of a pulmonary embolism, were detailed in a wrongful-death lawsuit filed this month by her family against American Airlines. The lawsuit alleges that the airline was negligent and ultimately contributed to her death because the pilot did not heed the doctor’s pleas to divert the plane and an onboard defibrillator and blood pressure monitor were faulty.

The lawsuit, which was filed in federal court in South Carolina on April 18, was brought by Oswell’s parents, Chris and Tina Starks, and her widower, Cory Oswell. In an interview today, her parents said they were still struggling with her death two years later.

“A decision was made not based on the human life that was on board or based on safety,” Tina Starks said. “Frustration doesn’t really describe how disappointed and heartbroken and just immensely discombobulating it has been.”

Chris Starks said the pilot faced an obvious choice when his daughter was gravely ill. “They should have landed at the very next possible opportunity,” he said.

A spokesman for American Airlines declined to discuss the specifics of the case. “We are deeply saddened by this event, and our thoughts and prayers continue to go out to Ms. Oswell’s family,” he said. “We are taking a look into the details of the complaint.”

Flight 102 was supposed to be the start of a new chapter for the Oswells, who had just wrapped up about a year living in Hawaii. Cory Oswell, 27, who was in the Army, was medically discharged and the couple were headed back to their home state, South Carolina, where they planned to live with her parents in Columbia, the capital.

After Brittany Oswell boarded the plane and sat down in her window seat, she called her mother to check in and said she would call again when they landed at Dallas-Fort Worth International Airport for their connecting flight. But the next call came from her husband.

“I could detect in his voice that it was very different,” Tina Starks said. “He said, ‘Ms. Starks, something happened.’”

Within several hours, her parents were by her hospital bed in the intensive-care unit of a Dallas-area hospital. Oswell had limited brain activity and was unconscious and on life support, her parents said. Doctors determined she had suffered a pulmonary embolism — a clot that blocks blood flow to the lungs — on the flight and then had multiple heart attacks. She died three days later.

“We still feel as though we are in a dream,” Starks said. “Everything still feels very surreal.”

Through his lawyer, Oswell declined to comment about the lawsuit.

The parents said their sadness turned to anger a few months after her death, when they heard the full story of what had happened on the flight. The doctor on board, who was not named in the lawsuit, told them about her frustrating attempts to use the plane’s faulty medical equipment and to get the pilot to land.

After Oswell collapsed in the lavatory, the doctor attempted to take her blood pressure, but the cuffs did not work, the lawsuit says. Then the pilot summoned the doctor to the cockpit, where she relayed the severity of Oswell’s condition and recommended the plane be diverted, according to the suit.

At that point in the flight, the lawsuit says, the plane was over New Mexico, with about two hours remaining in the flight. Her parents argued today that the plane should have diverted to Albuquerque.

Soon after the doctor left the cockpit and returned to Oswell, she stopped breathing and lost a pulse, the lawsuit says. The doctor opened the plane’s automated external defibrillator, attached the pads to her chest and tried to revive her with a shock, the lawsuit says. But despite three attempts, the device did not deliver a shock.

The lawsuit does not explain why the defibrillator malfunctioned.

“The doctor on board the plane informed us that the equipment was not operational,” a lawyer for the family, Bradford W. Cranshaw, said in an interview. “Those are questions we have for American Airlines.”