Thinking of flying for the holidays this year? Expect to pay more for airfare than at any other time in recent years.

Thanksgiving airfare prices are currently averaging $281 round trip, up 25% from last year, according to travel booking group Hopper. For Christmas travel, airfare prices are averaging $435 round trip, up 55% from last year and 19% higher than in 2019.

Those are the highest levels in at least five years, according to the website.

What's the cause? It's not just inflation, even though that's been at a 40-year high for most of 2022, and has pushed the price of goods and services up across the board. Look to the airlines. While carriers have rebuilt much of their passenger capacity as the Covid-19 pandemic ebbs, they still only have about 87% of the available seats they had in 2019, according to Hayley Berg, economist at Hopper.

"So you're still missing 15% of the flights and seats that would be otherwise taking off," Berg said.

At the same time, the demand for flights has continued to surge as households book travel that was waylaid by the pandemic. On its quarterly earnings call Friday, Delta Air Lines CEO Ed Bastian said demand for air travel "remains very strong."

"After two years of delaying travel, it is clear that consumers are getting out and traveling the world," Bastian said.

Global demand has also gotten a boost from people who are choosing to spend less on products and more on experiences, the Delta Air Lines chief executive said. Business and international travel are also regaining some momentum, albeit slowly according to research from the consulting firm Deloitte.

"Demand has not come close to being quenched by a hectic summer travel season," Bastian said.

Meanwhile, the cost of jet fuel remains elevated, thanks in large part to the war in Ukraine and a decrease in crude oil refining capacity.

"For airlines, the cost of flying each seat is higher than ever before, and for consumers, there are fewer seats available to buy and each is going to be more expensive," Berg said. "That is going to continue to drive up airfares."

Experts say the best way to get ahead of the price surges is to book as soon as possible.

"If you haven’t booked holiday travel already, get ready for some really painful sticker shock," said Scott Mayerowitz, executive editor at The Points Guy travel savings website.

Berg, the economist at Hopper, said travelers should also try to take advantage of any flexibility they might have in their schedules. Arriving or departing on weekdays, especially earlier in the week, can often result in savings even if it means staying an extra day or more.

If there's any good news, it is that the rate of delays and cancellations that bedeviled travelers earlier this year has been reduced, according to data from flight tracking group FlightAware.com. FlightAware spokesperson Kathleen Bangs said that airlines have been quietly hiring more workers to help meet customer demand, which has helped reduce disruptions.

Bangs, too, advises that planning early and staying flexible when planning travel is the best way to ensure a better travel experience.

"Right now demand is high, which means book your seats," she wrote in an email to NBC News.

If the price drops later, an individual can book at a cheaper price and get a refund (on a refundable ticket) or bank it as a future travel voucher if not refundable.