WASHINGTON >> The U.S. Federal Aviation Administration (FAA) said on Monday that unruly airline passenger incidents remain high, and the agency vowed to maintain a zero-tolerance policy.

There were 915 cases of unruly passengers reported in 2024 through June 9, including 106 cases of passenger disturbances due to intoxication, the FAA said. The number of unruly passengers spiked in 2021 to nearly 6,000 during the COVID-19 pandemic with the introduction of mask mandates — including 4,290 mask-related incidents — but still remains about twice that of 2020 or earlier levels.

Unruly passenger incidents fell last year by 15% to 2,075 as the FAA levied $7.5 million in fines, compared with 2,455 cases and $8.4 million in fines in 2022.

Growing concerns about unruly passengers come as airlines and the FAA are gearing up for a record summer of travel. Last month, the Transportation Security Administration (TSA) said it screened 2.95 million airline passengers on May 24, the start of the long Memorial Day weekend, the highest number ever on a single day

The FAA said last year that it referred 39 unruly passengers in 2023 to the FBI, bringing the total of such referrals for violent and threatening behavior on planes to more than 270 since late 2021.

U.S. Attorney General Merrick Garland directed the FBI to prioritize investigations of airline passengers committing assaults following a 500% spike in incidents in 2021.

In March, William Allen Liebisch, 43, of Cincinnati, Ohio, was sentenced to two-and-a-half years in prison after pleading guilty for interfering with a flight crew, the Justice Department said.

Liebisch carried a box cutter on a Tampa-bound flight and told a fellow Frontier Airlines passenger that he wanted to stab someone on board, prompting the pilot to make an emergency landing in Atlanta.

The FAA imposed the “zero tolerance policy” in January 2021 and said it would enforce it at least as long as the face mask order remained in effect. The agency opted to extend it indefinitely in April 2022.