(Bloomberg) -- Two passengers flying on separate airlines were hit with proposed fines on Friday following incidents in which they refused to wear masks and allegedly assaulted flight attendants.

The Federal Aviation Administration is seeking penalties of $15,000 and $7,500 in the cases, which occurred in August, it said in a press release. The FAA’s action is the strongest yet by the government to affirm airline policies requiring passengers to wear face coverings as a result of the Covid-19 pandemic.

The government hasn’t itself enacted a mask requirement, but the FAA said “federal law prohibits physically assaulting or threatening to physically assault aircraft crew or anyone else on an aircraft.”

In one case, a passenger on an Allegiant Air Inc. flight from Clearwater, Florida, to Mascoutah, Illinois, who had balked at instructions to wear a mask hit a flight attendant and grabbed the attendant’s phone while screaming obscenities, the FAA alleged. The flight was diverted as a result of the incident. The FAA is seeking the higher of the two penalties in this case.

In the second case, a person on a SkyWest Airlines Inc. flight from Atlanta to Chicago removed his or her face covering in spite of being told to wear it, “continually bothered other passengers,” and grabbed a flight attendant’s buttock, the FAA said.

While the law allows criminal charges for interfering with a flight crew, the people were charged with civil penalties only. The people can contest the fines, which are often lowered in settlement agreements. The FAA doesn’t identify the names of individuals it has charged with civil violations.

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