A flight attendant for American Airlines was hospitalized after a passenger allegedly attacked her on Wednesday, in what the company’s chief executive called “one of the worst displays of unruly behavior we’ve ever witnessed.”

The incident occurred during a flight from John F. Kennedy International Airport in New York to John Wayne Airport in Orange County, California. The pilots were forced to divert the flight to Denver, where the passenger was detained.

According to Julie Hedrick, president of the Association of Professional Flight Attendants, which represents those who fly for American Airlines, the flight attendant apparently bumped the passenger while moving through the first-class cabin. The flight attendant apologized, but the passenger got up, confronted her in the aircraft’s galley, and punched her in the face, according to Hedrick.

The flight attendant was taken to a hospital for treatment of broken bones in her face, according to Hedrick. She was eventually released.

The incident echoed one from earlier this year, when a Southwest Airlines flight attendant allegedly was punched in the face by a passenger. The attacks follow an increase in incidents in which passengers yelled obscenities, pushed and shoved flight attendants, harassed other passengers, or even attempted to open the cockpit door.

Problem passengers, according to Hedrick, are not a new phenomenon, but recent incidents have put flight attendants on edge. The Federal Aviation Administration, which is in charge of enforcing airline rules, has seen a sixfold increase in unruly passenger investigations over the last two years. According to Hedrick, the number of incidents involving unruly passengers has decreased since summer highs. “It doesn’t matter when something like this happens,” she said.

American Airlines CEO Doug Parker said in a strongly worded video message on Instagram that the airline would push to have the passenger “prosecuted to the fullest extent possible.” He stated that the individual would be barred from traveling on American Airlines.

“This type of behavior has to stop,” Parker said, adding that the airline is also working with the FAA, which can levy fines of up to $50,000 in such cases.

During the coronavirus pandemic, the number of airline passengers cited for “unruly behavior” has skyrocketed. Some of the clashes are sparked by disagreements over federal regulations requiring passengers to wear masks when boarding planes. According to the FAA, more than 3,500 of nearly 5,000 reports of unruly behavior this year involve mask disputes. Others have involved alcohol, causing some airlines to temporarily halt sales.

The agency implemented a “zero-tolerance” policy for bad behavior on flights in January. According to the FAA’s most recent statistics, the agency is investigating 923 incidents and has initiated enforcement action in 216 of them. The FAA investigated 146 cases of unruly behavior among passengers in 2019, when the number of people traveling was at an all-time high.

According to Hedrick, there is no evidence that the incident on Wednesday involved a mask dispute. She also stated that it is unclear whether alcohol played a role. American is one of several airlines that restricts alcohol sales on domestic flights. Alcohol is available in the airline’s first-class cabins.

Denver International Airport officials referred calls to the FBI’s local office, which is investigating the incident. Parker stated in his video message that the passenger had been arrested. Hedrick also stated that the union is investigating an incident that occurred in Honolulu on Wednesday. During the incident, a passenger allegedly spit on and slapped a flight attendant as she exited the plane.

She stated that her union and others are still pushing for a federal “no-fly” list that would prevent such passengers from flying. Airlines keep their own “no-fly” lists, which are not shared with other carriers. According to Hedrick, aviation workers are also advocating for increased police presence and more oversight of what happens to passengers who are arrested.