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American Airlines and United Airlines airplanes wait at Newark Liberty International Airport's Terminal A in New Jersey. Incidents of unruly behavior aboard planes have gone down since 2021, but some incidents are still so bad that the FAA brings in the FBI.
CNN  — 

Some unruly airline passengers get so unruly that the FBI gets involved.

Nearly two dozen more passengers – some accused of physical or sexual assault on fellow flyers and flight crew members – now might face potential criminal charges, bringing the number of passengers facing charges so far in 2023 to just over three dozen.

On Tuesday, the Federal Aviation Administration said that in the second quarter of this year, it sent 22 new cases of unruly passenger incidents on board commercial flights to the Federal Bureau of Investigation for “criminal prosecution review.” Since the start of the year, 39 cases have been referred to the FBI.

Notably, the referrals include a passenger who allegedly airdropped a bomb threat to other passengers in October of last year.

In another case dating back to July 2022, the FAA says a passenger “sexually/physically assaulted an unaccompanied minor.”

The FAA says a passenger in April of this year “yelled, cursed, threw objects at passengers and had to be restrained in cuffs.”

The FAA can only assess civil fines against passengers for violating its zero-tolerance policy for unruly behavior on board flights, regularly referring the most egregious cases to the Justice Department for possible charges. The policy went into effect on January 13, 2021, to address an increase in unruly passenger incidents. The policy skips warnings or counseling and goes directly to penalties, which can include heavy fines and jail time.

Cases that make it to the FBI

In 2021, as air travel ramped up from historic lows prompted by the outbreak of the Covid-19 pandemic, nearly 6,000 incidents of unruly behavior were reported to the FAA, compared with 1,161 before the pandemic in 2019.

In 2022, reports dropped to 2,455. So far this year, 1,177 incidents have been reported.

A fraction of reported incidents are investigated, and a smaller number prompt enforcement action, often in the form of fines. A small number of cases make it to the FBI for possible criminal prosecution. More than 270 cases have been referred to the FBI since 2021, according to the FAA.

Last year, a man charged with groping a flight attendant was sentenced to six months in prison and another unruly passenger received a four-month prison sentence.

The number of unruly passenger incidents has gone down “80 percent,” the FAA says, since hitting a peak in 2021, “but unacceptable behavior continues to occur.”

CNN’s Marnie Hunter contributed to this report.