(CNN) — The holiday travel season in the United States this year is looking a lot more like 2019.
Airlines are projected to carry 6.4 million passengers, according to travel organization AAA. That's about triple the number from last year when the pandemic significantly curtailed holiday air travel.
Overall, AAA estimates more than 109 million Americans will travel over the long Christmas and New Year's week -- 92% of 2019 travel volume.
Transportation Security Administrator David Pekoske predicted that December 23 and January 3 will be the busiest days of the end-of-year crush at airports.
But there's a wild card in play: Omicron.
The new variant, designated a "variant of concern" over the Thanksgiving travel period, adds an extra layer of uncertainty as people set out on December and January trips.
Travelers queue up at a security checkpoint on November 23, 2021, at Denver International Airport.
What medical experts are saying about gathering for the holidays
If you're vaccinated, you should be able to go ahead with holiday plans -- even with Omicron circulating in the United States, according to Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases.
"People ask you, 'Well, what about the family setting?' If you're vaccinated, your family members are vaccinated, you should feel comfortable in the setting of the holiday season to have dinners and social events at home," Fauci told CNN's Wolf Blitzer on Wednesday.
"I mean, nothing is 100%, but when you talk about the relative risk when you're dealing with vaccinated and, particularly, boosted people, you can feel comfortable enjoying the holiday," he said.
Traveling does increase the risk of getting infected, he said earlier this month, but wearing a mask and getting vaccinated and boosted helps protect travelers moving through busy spaces.
Dr. Peter Hotez, a vaccine specialist and dean of tropical medicine at the Baylor College of Medicine in Houston, is concerned about holiday travel for his family. He told CNN's Alisyn Camerota and Victor Blackwell on Wednesday that he has pared down their plans.
"I don't want to be the Dr. Grinch that stole Christmas," Hotez said, but he canceled a planned visit from in-laws. "Unfortunately, I had to ask them not to come because I thought that it was a little too risky for them in terms of travel with all the Omicron circulating."
Whether to travel or not is a personal calculation, says CNN Medical Analyst Dr. Leana Wen.
"There are a lot of unknowns, so I think that depends on people's individual risk tolerance. There will be some people who are OK with the unknowns and who are generally healthy, fully vaccinated and aren't that worried," Wen said. "But there are other people who because of their own medical situation or because of risk factors might feel differently."
And while there's still a lot to learn about Omicron, health experts have also underlined one of the things we do know right now: the Delta variant is still a big threat.
As the holiday travel season revs up again, here's more of what experts advise for safer, smoother trips:
The TSA expects traveler volumes near pre-pandemic levels this season.
Anna Moneymaker/Getty Images
Smoothing the way, travel-wise
The TSA is encouraging air travelers to sign up for TSA PreCheck, the expedited screening program that doesn't require members to remove their shoes, belts, liquids, laptops or light jackets.
Other tips from the TSA:
-- Avoid airport rush hours, typically 5 to 7 a.m. and 4 to 6 p.m.
-- Arrive two hours before domestic flights and three hours for international flights
-- Respect TSA officers, flight crew and other frontline workers and pack firearms properly to avoid fines.
Travel organization AAA recommends travel insurance.
"Get that trip insurance and that airline insurance if you can. That little box you often skip, click it this year because we don't know what staffing levels are going to be like for the airlines and for TSA," AAA spokesperson Andrew Gross said right before the Thanksgiving rush.
And make sure your vehicle is ready if you're driving. AAA suggests getting key components such as the battery, fuel system, tires, brakes and fluid levels checked before a road trip.
For those traveling with unvaccinated people, the CDC suggests safer options such as road trips with few stops and direct flights.
Logistical considerations for international travel
Those travelers with international plans have more to consider. Ever-shifting restrictions in countries all over the world and the new US requirement to take a test within one day of a return flight's departure for the United States could mean unexpected wrinkles.
"This is a very dynamic situation, and travelers should consider how important the trip is to them and have a plan B and a plan C," said Wen, who is an emergency physician and professor of health policy and management at the George Washington University Milken Institute School of Public Health.
Travelers walk through the main concourse at Reagan National Airport in Arlington, Virginia, on November 23 during the Thanksgiving holiday period.
Drew Angerer/Getty Images
"They should think through all the scenarios for what could happen. Let's say that they end up in a country that is now going to implement a mandatory quarantine on arrival. How will they cope with that? Is it worth going?"
US embassies provide country-specific information for American citizens, including whether tests in a particular destination are reliably available within the one-day period required for their return.
Getting there safely. And what happens next
Wen and Dr. William Schaffner, a professor of infectious diseases at Vanderbilt University Medical Center, stress that what travelers intend to do at their destinations is likely to pose a greater risk than the journey itself, provided travelers wear masks in transit and socially distance as much as possible.
A trip that involves a lot of shopping and going to the theater, eating in crowded restaurants and going to your favorite New York City bar increases your chances of becoming infected, Schaffner said.
"If you want to do all that, yes, you're assuming more risk," he said.
Schaffner added that it's important to get vaccinated against influenza, which is picking up in the United States.
People should be wearing a high-quality mask -- N95, KN95 or KF94 -- anytime they're in crowded indoor settings with people of unknown vaccination status, Wen said.
Traffic fills North Capitol Street on November 23 in Washington, DC.
Anna Moneymaker/Getty Images
With the rise of Omicron, Wen suggests that indoor gatherings should have two out of these three elements: vaccination, testing and masking.
"If everyone is unmasked and eating together, they should be vaccinated and tested the day of, for example."
When everyone who's eligible for vaccination and boosters gets them, it also helps protect kids younger than 5 who aren't eligible for vaccination yet.
If a gathering involves immunocompromised family members or unvaccinated children, or both, Wen suggests that everyone quarantine for at least three days before getting together and taking a rapid test just before seeing each other.
"That would reduce the risk for everyone," she said. The CDC recently updated its guidance on self-testing as one risk-reduction strategy.
Schaffner said his family all took tests before gathering for Thanksgiving.
"And so not only are we vaccinated and boosted, but we tested negative," he said. "Now if you start taking control like that, then you can do your travel and your reunions and your social events at very low risk."