The president of the union that represents American Airlines flight attendants has urged members to remain "extra vigilant" on flights departing the Washington area in the coming days.
Meanwhile, airlines say that they have increased staffing at D.C.-area airports as a precautionary measure while the city roils from the deadly riot by President Trump supporters on the U.S. Capitol Wednesday.
Related report: Travel industry leaders condemn siege on U.S. Capitol
"As safety professionals, we are well trained in handling inflight disruptions, but we should never find ourselves having to deal with politically motivated verbal or physical altercations onboard," Association of Professional Flight Attendants president Julie Hedrick wrote to members Wednesday evening. "Please continue to maintain situational awareness, and attempt to deal with all safety and security issues on the ground."
The statement followed several tense incidents on planes carrying Trump supporters to Washington this week that were recorded and shared on social media.
In one Tuesday night incident on American, for example, passengers screamed obscenities at one another as a flyer projected a Trump 2020 image on the aircraft walls.
American said it is reviewing the incident, but hasn't said whether any action will be taken against passengers.
Other Twitter postings show Trump supporters leading chants on flights. One group of flyers on a Tuesday flight from San Francisco to Washington sang the national anthem before moving on to chanting Trump's name. Video from a Southwest flight showed a number of unmasked flyers chanting, "fight for Trump."
With many of the Capitol rioters slated to take to the air for return trips Thursday and in coming days, United and American both said they have beefed up security.
"[W]e have increased staffing at Washington-area airports and are in close contact with appropriate law enforcement agencies, including TSA and [Metropolitan Washington Airports Authority] Police, to continuously monitor the situation in real time," United said in a statement. "We will continue to enforce our strict mask policy, as we have done for every flight since the spring of last year."
American offered a similar statement and added that at least through Thursday night it will suspend alcohol sales in the first-class cabin on flights to and from the Washington area. (Main cabin alcohol sales are already suspended networkwide due to the Covid-19 pandemic).
Both air carriers have also moved layover crews out of the downtown Washington area, with American moving flight attendants specifically to airport-area hotels.
In a statement, the Association of Flight Attendants-CWA, which represents flight attendants for United and nearly 20 other airlines, said that some of the people who participated in the insurrection flew on planes that members crewed.
"Acts against our democracy, our government and the freedom we claim as Americans must disqualify these individuals from the freedom of flight," the union said.