FAA to make zero-tolerance policy against unruly passengers permanent

• The four largest airlines in the U.S. — United, American, Delta and Southwest Airlines — dropped their masking requirements after the Transportation Security Administration announced that it would no longer enforce a mandate.

What they're saying: "Behaving dangerously on a plane will cost you; that’s a promise," acting FAA administrator Billy Nolen said.

• “Unsafe behavior simply does not fly and keeping our Zero Tolerance policy will help us continue making progress to prevent and punish this behavior.”

The big picture: The FAA originally implemented the policy last year after a "disturbing increase in incidents" of passengers disrupting flights with "threatening or violent behavior," Axios' Joann Muller writes.

• The policy, combined with the agency's public awareness campaign, has helped reduce the incident rate by more than 60%, according to the FAA.

By the numbers: There have been 1,233 reports of unruly passengers as of this past Tuesday, per the FAA. These included 797 mask-related incidents.

• From the reports, 370 investigations have been launched, 192 FAA enforcement cases initiated and 80 cases have been referred to the FBI for criminal review, according to the aviation agency.