Transportation Secretary Pete Buttigieg on Sunday urged travellers to respect flight attendants and other crew members who enforce federal mask mandates on planes, pledging strict federal enforcement against such abuse at a time of increasingly unruly behavior by passengers.

“The flight crews and other workers you encounter, they’re doing their job,” he said. “They’re following regulations and they’re there to keep you safe. It is absolutely unacceptable to ever mistreat a transportation worker.

“And of course, there’s very serious fines and enforcement around that,” Buttigieg added.

Buttigieg said the federal mask mandate, which remains in effect on planes, buses and trains until Sept. 13, continues to be driven by public health considerations. He stressed that travellers should abide by it as both a matter of safety and respect to transportation workers.

“Part of it has to do with the unique conditions of the physical space,” Buttigieg said, explaining the extra COVID-19 precautions for crowded spaces. “Part of it has to do with the conditions of it being a workplace, and folks who really don’t have a choice about being there, the way it is in some other cases.”

Centers for Disease Control and Prevention guidelines say that fully vaccinated people can go without face coverings inside and outside various public areas.

“These rules and regulations and these bodies of guidance always evolve with the science,” Buttigieg said.

His admonition comes after the Federal Aviation Administration announced last week it was proposing civil penalties as high as US $15,000 against five passengers for violations that included allegedly assaulting and yelling at flight attendants.

Southwest Airlines last week also banned a woman accused of punching a flight attendant shortly after a plane from Sacramento, California, landed in San Diego on May 23. The airline said the passenger ignored instructions from the flight attendant before assaulting her. San Diego Harbor Police arrested Vyvianna Quinonez, 28, and charged her with felony battery.

The FAA says reports of unruly passenger behavior has been on the rise this year as more travellers return to the skies. According to the agency, from Jan. 1 through May 24, there were roughly 2,500 reports of unruly behavior by passengers, including about 1,900 reports of people refusing to comply with the federal mask mandate.

Buttigieg spoke on ABC’s “This Week” and CNN’s “State of the Union.”