The country's largest flight attendant unions on Wednesday expressed safety concerns over politically motivated disruptions on flights after a pro-Trump mob stormed the Capitol building, demanding that the results of the presidential election be overturned.

The unions' comments came after at least two on-board disruptions on Washington D.C.-bound flights, including a Delta Air Lines flight carrying Republican Sen. Mitt Romney of Utah, during which some passengers chanted "traitor." Delta said it was aware of the incident and that "our crew quickly engaged and resolved the issue." A spokeswoman for the senator didn't comment.

"The mob mentality behavior that took place on several flights to the D.C. area yesterday was unacceptable and threatened the safety and security of every single person onboard," said Sara Nelson, president of the Association of Flight Attendants-CWA, which represents some 50,000 cabin crew members at United, Alaska and more than a dozen other carriers.

The riots at the Capitol "create further concern about [participants'] departure from the D.C. area," Nelson said. "Acts against our democracy, our government and the freedom we claim as Americans must disqualify these individuals from the freedom of flight."

On an American Airlines flight to Dulles International Airport earlier this week, passengers shouted and cursed at each other, forcing the flight attendant to turn up cabin lights that had been dimmed and ordered passengers to their seats, according to a video shared by Twitter user @MaranieRae who said she was on the flight.

American is reviewing the incident, said spokesman Curtis Blessing. "We applaud our outstanding crewmembers for their professionalism in de-escalating a tense onboard situation and getting our customers to their destination safely," he said.

Julie Hedrick, president of the Association of Professional Flight Attendants, which represents American Airlines' more than 25,000 flight attendants, said in a statement that the union is "incredibly concerned about recent politically motivated incidents on board passenger aircraft.

"Regardless of one's political beliefs, the cabin of a commercial aircraft must, out of necessity, be a calm environment for the safety of everyone on board," she said.

Flight attendant unions called for zero tolerance for such incidents. Interfering with the duties of a flight crew member is against the law and unruly passengers can be fined up to $35,000.

Airlines said they are taking several precautions to protect employees, including moving flight crews to airport hotels so they can avoid locations in central Washington D.C.

American Airlines is also not selling alcohol on board flights to and from the Washington D.C. area and has increased staffing at D.C.-area airports, American spokesman Blessing said.

Correction: Interfering with the duties of a flight crew member is against the law and unruly passengers can be fined up to $35,000. An earlier version misstated the figure.