Two Spirit Airlines agents were injured on Sunday after three passengers "attacked them" while trying to board a flight from Detroit to Atlanta "without authorization" on Sunday, the airline said.
Spirit Airlines told ABC News that the group became combative after the agents asked the passengers to verify that their carry-on bags met the airline's luggage size requirements.
"The agents attempted to calmly defuse the situation," Spirit said in a statement, "but were physically assaulted by these passengers as they closed a door to stop them from boarding the aircraft."
The airline confirmed one of the agents had to be transported to the hospital.
"All of us at Spirit wish the agents a speedy recovery and thank them for their courage and professionalism," the statement continued.
Spirit said those involved in the "attack" were arrested by law enforcement. Those passengers are also banned from any future travel on the airline.
"This violent behavior is completely unacceptable and has absolutely no place in airports or any other place of business," Spirit said.
The incident comes less than a week after the Federal Aviation Administration (FAA) announced it will begin handing down stricter punishments to unruly airline passengers without a warning, including "fines of up to $35,000 and imprisonment."
FAA Administrator Steve Dickson signed the order Wednesday directing the agency to take a "zero-tolerance policy" in unruly passenger cases after the agency saw a "disturbing increase in incidents" of passengers disrupting flights with "threatening or violent behavior."
The FAA's new policy will remain in effect through March 30.
"We can always make it a longer time period," Dickson told ABC News.
The agency said it has "initiated more than 1,300 enforcement actions against unruly passengers" within the last decade, "including recent cases for allegedly interfering with and assaulting flight attendants who instructed them to wear masks."