An American Airlines flight from New York to California was diverted to Denver after a passenger assaulted a flight attendant authorities said. A source familiar with the details of the incident said “the attack was unprovoked,” saying the passenger went to the back of the plane and punched the flight attendant twice in the face and broke her nose.

Flight 976 was heading Wednesday from John F. Kennedy International Airport to John Wayne Airport in Santa Ana when it landed at Denver International Airport and taxied to the gate.

The passenger was removed, the airline said, and the flight continued on to California. The flight attendant was reportedly taken to a hospital, but details on her condition weren’t immediately released.

“We are outraged by the reports of what took place on board. Acts of violence against our team members are not tolerated by American Airlines,” the airline said in statement.

CEO Doug Parker said the airline is supporting the injured flight attendant and banning the man accused of assaulting her from flying on the airline again.

Law enforcement was investigating the assault and the Federal Aviation Administration said it would investigate as well.

The assault comes amid a surge in unruly airline passengers who sometimes become violent.

The FAA adopted a zero-tolerance policy for such passenger behaviour on board flights earlier this year. The agency said in August it had issued more than US $1 million in fines to unruly passengers in 2021. The FAA said there had been 4,941 unruly passenger reports this year.

A survey by the Association of Flight Attendants released in July found that, of the 5,000 flight attendants surveyed, 85% said they’d dealt with unruly passengers in 2021.

Disruptive passengers had used sexist, racist and/or homophobic language, according to 61%, while 17% said they’d been a victim of a physical attack.