When the Omicron version of the coronavirus made news in late November, Carla Benton, a Chicago-based book copy editor, was planning for a Christmas trip to Europe.

Due to constantly changing travel regulations and testing requirements, she canceled her foreign vacation plans and instead chose to stay in the United States and visit her sister in Houston, Texas. Benton finally opted to cancel his vacation plans and spend the Christmas in Chicago.

“I had hoped to be able to improvise portions of my journey,” Benton stated. “I was concerned about the possibility of a surprise positive test and quarantine overseas, even though I’m fully vaccinated and taking measures here in Chicago.”

For the previous four days, the Transportation Security Administration has checked more than 2 million individuals each day, although that number is still down around 15% from pre-pandemic levels. Even as COVID-19 cases in the United States rise and Omicron spreads, the TSA plans to inspect 30 million travelers between Monday and January 3.

In recent weeks, airlines have reported an increase in cancellations. Despite this, millions of Americans are anticipated to hit the roadways and board planes to spend the holidays with family and friends.

Delta Air Lines Inc said last week that Omicron had slowed international bookings as many countries imposed new travel restrictions.

However, the airline’s chief executive officer, Ed Bastian, told CNBC that “Omicron (is) not going to impact our holiday bookings.”

United Airlines is flying its busiest schedule this month since the start of the pandemic, with more than 4,000 flights per day on average during the year-end holidays. The airline said it added more than 200 daily domestic flights to meet holiday travel demand.

Similarly, Southwest Airlines said on Monday the airline is encouraged by holiday demand trends.

American Airlines incoming Chief Executive Robert Isom told Reuters the airline’s domestic business remained strong but the new travel restrictions had dampened demand in some international markets.

Nationally, COVID cases rose 9% in the past week but are up 57% since the start of December, according to a Reuters tally.

The spike in U.S. COVID-19 cases is causing some worry about the future of travel.

Omicron fears and new travel restrictions have prompted a rise in global hotel cancellations, according to online hotel search firm Trivago.

As cases continued to climb, investors pushed airline and travel stocks lower on Monday. United Airlines dropped 3.3%, while Royal Caribbean Group slipped 3.4% after 48 people on its Symphony of the Seas cruise ship tested positive for COVID-19.

And Carnival Corps said on Monday Omicron is already hitting the cruise line’s near-term bookings.

But more than half of Americans still did not intend to cancel their holiday travel plans as of early December, according to a poll from market research firm Ipsos released Dec. 7, when Omicron was already spreading in the United States.

The American Automobile Association still expects this year to bring holiday travel in line with 2017 volumes, following the dramatic decrease in 2020.

“Our forecast focuses on domestic travel, which we do not expect to be affected to the extent that international travel might,” said Ellen Edmonds, public relations manager at AAA.

Major U.S. airports, preparing for a surge in holiday travelers, are maintaining their existing COVID-19 safety protocols like mandatory masking and extra cleaning.

Denver International Airport spokesperson Alex Renteria said the airport still expects an uptick in travel over the holiday period, in line with high passenger volume since Thanksgiving.

In the first half of December, passenger traffic at Miami International Airport was up 9% compared to the same period in 2019, according to communications director Greg Chin. Travel through the Florida airport is surpassing even pre-pandemic levels, with the average number of daily departing flights up nearly 12% compared with December 2019.