U.S. airlines and their unions want the Justice Department to send a strong message against the rise in unruly passengers with additional federal criminal charges.

Several airline trade groups and unions sent a letter Monday to Attorney General Merrick Garland calling for criminal enforcement that goes beyond the increase in civil charges filed so far this year by the U.S. Federal Aviation Administration.

“The federal government should send a strong and consistent message through criminal enforcement that compliance with federal law and upholding aviation safety are of paramount importance,” the groups said in the letter.

The Justice Department didn’t immediately respond to requests for comment on the letters.

The FAA says it has been aggressively acting against people who violate federal regulations. It has sought more than $300,000 in fines in more than 20 cases.

“The FAA’s zero tolerance policy remains fully in place, and we will continue to work with local law enforcement and the DOJ to make it clear that unsafe and unruly behavior simply does not fly,” the agency said in an emailed statement.

There have been almost 3,000 reports of unruly passengers on flights this year, a dramatic increase over previous years, according to the FAA. The agency has attempted to fine dozens of people, many of whom refused to wear masks.

Federal law makes it a crime to assault or intimidate airline pilots or flight attendants, though violations have traditionally been handled with non-criminal civil prosecutions by the FAA.

“Making these prosecutions public will put a spotlight on the serious consequences when breaking the law and will act as an effective deterrent against future onboard disruptions,” the groups said.

The organizations behind the letter include Airlines for America, a trade group for large carriers, the largest U.S. flight-attendant unions and groups representing other airlines.

A4A’s president Nicholas Calio asked FAA Administrator Steve Dickson in a separate letter on Monday to coordinate with the Justice Department and to refer cases for criminal charges where appropriate.