The number of fliers this year will approach pre-pandemic levels, according to the Transportation Security Administration. However, experts said staffing shortages and a storm on the horizon threaten to disrupt Americans’ holiday plans.

“One of the things folks have not accounted for is that conditions have changed,” Willis Orlando, senior product operations specialist at Scott’s Cheap Flights, told ABC News. “If you’re checking in for a flight and it’s an international flight, airline agents now have to check many more layers of documentation depending on where you’re going. So those lines are going to take longer. Add to that lingering staffing shortages and you have a recipe for long lines and delays.”

Here’s what you need to know about the best and worst times to travel:

Sunday after Thanksgiving projected to be busiest travel day of year

The TSA is prepping for a busy Thanksgiving travel period — with travel volumes expected to reach 2019 pre-pandemic levels. The agency said it expects the Sunday after Thanksgiving to be the busiest travel day of the year — with an estimated 2.4 million passengers on Nov 28. It expects 2-2.1 million passengers on Nov. 23, 24, 27, and 29.

Despite a looming vaccine mandate on Monday for all TSA agents, the agency insists it’s “confident” that it has the staffing needed to manage the holiday travel crush.

But experts still recommend heading to the airport early next week.

“Don’t count on fast check-in lines,” Orlando said. “Get there two hours before a domestic flight and two and a half or three hours before an international flight. It’s better to get there early and be prepared than to get there late and be sorry.”

Hartsfield-Jackson Atlanta International Airport will be busiest US airport

Hartsfield-Jackson Atlanta International will be the busiest airport on Thanksgiving weekend, with 154,000 departing seats on Wednesday, Nov. 24, according to travel booking app Hopper.

Atlanta is followed by Dallas Fort Worth International Airport and Los Angeles International Airport as the second and third busiest airports, with 103,000 and 101,000 passengers expected respectively.

All three airports are expected “to be really busy” on Wednesday morning, Hopper Economist Adit Damodaran told ABC News.

“The Wednesday before Thanksgiving — Nov. 24 — will be the busiest travel day to depart at most airports across the U.S., especially in the morning,” Damodaran said.

Majority of Americans will drive to their destination over Thanksgiving.

AAA predicts 53.4 million people will travel on the roads and in the skies for the Thanksgiving holiday, which is up 13% from 2020. This year’s forecast marks the highest single-year increase in Thanksgiving travelers since 2005, bringing travel volumes close to pre-pandemic levels in 2019, according to AAA.

Of those 53.4 million, AAA says a majority of them, 48.3 million, will hit the road.

Worst time to drive is Wednesday afternoon.

Data from analytics company INRIX shows that anytime after noon all the way through 8 p.m. Wednesday will see the most congested roads.

The Sunday after Thanksgiving could have some traffic jams as well from 1 p.m. to 7 p.m.

In Atlanta, congestion during peak times will reach a high of 340% over normal, in New York a whopping 482% and in Los Angeles — 385%.

If you are driving, experts said to also be mindful you might be paying more at the pump than you’re used to at $3.35 per gallon.

“We’re just cents away from the highest Thanksgiving gas prices ever recorded,” Patrick De Haan, head of petroleum analysis at GasBuddy, said in a press release. “With global oil demand surging this year as the pandemic has eased, we find ourselves in unfamiliar territory – some of the highest Thanksgiving gas prices on record.”