WASHINGTON (AP) — U.S. officials said Tuesday they have referred 22 more cases involving unruly passengers on airline flights to the FBI for possible criminal charges.

The allegations include sexually assaulting female passengers, attacking flight attendants, trying to break into the cockpit, making terror threats, and smoking in airplane lavatories.

The Federal Aviation Administration said the incidents happened as far back as late 2021 and as recently as April of this year.

The FAA can seek fines of up to $37,000 against unruly passengers, but it lacks authority to file criminal charges; that is why the agency refers some cases to the FBI.

Reports of passengers acting up on flights peaked in 2021, with many of the roughly 6,000 incidents involving anger over a since-dropped mask requirement. The number dropped under 2,500 last year and under 1,200 so far this year, the FAA said.

The FAA said it has referred more than 270 cases to the FBI since late 2021.