• Airlines have banned more than 2,000 travelers for refusing to follow mask
• Carriers and the FAA have promised to crack down on unruly travelers and enforce mask policies.

Cursing at flight attendants. Harassing lawmakers. Refusing to wear masks.

Tensions are rising in air travel, prompting safety concerns as airlines continue to reel from the coronavirus pandemic's impact. In the wake of the deadly riot at the U.S. Capitol and a spate of disruptions on board, airlines and the Federal Aviation Administration promised zero tolerance for bad behavior. Airlines, airports and the Transportation Security Administration are adding staff and increasing security measures ahead of president-Elect Joe Biden's inauguration on Wednesday.

"As if aviation needs any more kicks to the head right now," said Jeff Price, an aviation safety specialist and professor in the aviation and aerospace department at Metropolitan State University of Denver, said of the trend.

Delta Air Lines banned six travelers from a Jan. 5 flight from Salt Lake City to Washington D.C. Several passengers shouted "traitor" at Utah Republican Sen. Mitt Romney for not challenging the results of the November presidential election, according to a video of the incident that was shared on social media. On Jan. 8, Alaska Airlines said it banned 14 travelers who were "non-mask compliant, rowdy, argumentative and harassed our crew members" from a Washington D.C.-Seattle flight, spokesman Ray Lane said, apologizing to other passengers who were uncomfortable on the flight.

Delta CEO Ed Bastian last week said such incidents are extremely rare and that most of its customers don't pose a problem, but the carrier warned it won't accept disruptive behavior.

"Those who refuse to display basic civility to our people or their fellow travelers are not welcome on Delta," Bastian said in an employee memo on Friday. "Their actions will not be tolerated, and they will not have the privilege of flying our airline ever again."

On a Jan. 5 American Airlines flight a traveler projected "Trump 2020" on a cabin wall, while travelers got into a profanity-laced shouting match, prompting a flight attendant to turn on the lights and order people to their seats. A pilot on a Jan. 8 American flight, from Washington-to-Phoenix, warned travelers he would "put this plane down in the middle of Kansas and dump people off" to convince passengers to "behave."

The FAA last week said it would fine travelers the maximum $35,000 for unruly behavior, instead of a usual procedure of a warnings. FAA Administrator Steve Dickson's order on Wednesday came after the series of reports of flight disruptions by what appeared to supporters of President Donald Trump and more cases of travelers who refuse to wear masks.

"These incidents have stemmed in some cases from refusal to follow airline policies on face coverings and also we saw a trend after after the breach of the Capitol last week," Dickson told CNBC's "Squawk Box" on Thursday. "This is about flight safety. Anytime we see a trend like this we need to take action."

Airline passengers are legally obligated to follow crew member instructions. Unruly passenger behavior or interfering with crew's duties is against the law.

"First strike and you're out," said Sara Nelson, president of the Association of Flight Attendants-CWA, which represents 50,000 flight attendants at more than a dozen airlines. "This will help serve as a deterrent to unruly travelers who had been bucking the rules of aviation safety."

Even before the Capitol riot, the rate of cases of unruly passenger behavior had been on the rise.

From January through the end of November, the latest available data, the FAA pursued 108 enforcement actions for such behavior. That put it at a rate of 3.1 per 10 million enplaned passengers on U.S. airlines, double last year's rate and the highest since 2004.

There are far more cases that don't get reported because they are resolved on board, labor unions say.

One issue that has increased stress for some crews on board is getting passengers to wear masks, which are required by airlines to fly during the pandemic. While there is no federal mandate, passengers are required to both follow crew instructions and attest that they will comply with airline policies to wear one before they fly.

Some disputes over masks have led to reports of violence on board.

In August, a passenger on an Allegiant Air flight from Clearwater, Florida allegedly screamed obscenities and hit a flight attendant, while the cabin crew member talked to the captain about the traveler's behavior over a face-mask dispute, according to a report last month from the FAA, which recommended a $15,000 fine.

"The passenger in question has been banned and informed they are no longer welcome to fly Allegiant," a spokeswoman for the airline said.

On a SkyWest flight from Atlanta to Chicago, also in August, a passenger removed their face covering, bothered other passengers and "grabbed a flight attendant's buttock as she walked by the passenger's row of seats," the FAA said.

But even less severe cases have gotten travelers put on airlines' no-fly lists.

Delta has said it's banned more than 800 travelers for refusing to wear a mask. Alaska has banned more than 300, while United Airlines has banned more than 615 people. American and Southwest declined to say how many people they have banned so far.

One problem is how mask wearing in the pandemic is that wearing one has been politicized, as many measures to stop the spread of Covid has since the virus showed up in the U.S.

Wendy Wood, a psychology and business professor at the University of Southern California, said people who usually wear masks generally don't need reminding.

"They do it automatically," Wood said by email. When new rules are introduced that are unclear or politicized "then people who don't typically follow them in other contexts can feel pushed around and can get angry," she said.

On Jan. 1, 1988, the first day of a federal ban on cigarette smoking on domestic flights of less than two hours, several people "lit up anyway," on a TWA flight to Los Angeles, according to a New York Times story at the time. Federal law banned smoking on all commercial passenger planes two years later.

"We're basically playing babysitter for adults," said a flight attendant for a major U.S. airline, asking that their name be withheld for concerns over job security.