Over Thanksgiving, U.S. airlines experienced the biggest travel surge since before the COVID-19 pandemic began. Airports, planes, and parking lots were packed with travelers visiting family and friends over the Thanksgiving holiday weekend.

But now that travel is finally picking up again, airlines face a new challenge with the emergence of Omicron, a new COVID variant. Scientists in South Africa first discovered Omicron, and the World Health Organization (WHO) has identified it as a “variant of concern.”

Health officials worry it could be more easily transmissible due to its large number of mutations. On Friday, airline and travel stocks fell due to concerns over the variant and potential travel restrictions in the future.

How will Omicron impact holiday travel?

From Nov. 22 through Sunday, more than 14 million people passed through TSA. On Thanksgiving alone, TSA screened over 2.5 million people. This number is 15% lower than the number of passengers TSA screened in 2019, but the largest number of travelers seen since before the pandemic began.

Airlines offered flight attendants and staff additional pay or bonuses to work over the holiday. American Airlines, which offered its flight attendants triple pay for peak days, said it flew 5.6 million passengers from Nov. 19 through Sunday.

It’s been a long road to recovery for the travel industry, which took a major hit during the pandemic. But news of the Omicron variant has the potential to undo all of the progress that’s been made.

When Omicron was first detected last week, countries immediately began restricting international travel. Starting on Monday, the U.S. is temporarily banning visitors from South Africa. Israel has banned foreign visitors for two weeks, and the U.K. will require travelers to take a PCR test upon arrival.

Are travel restrictions the answer?

The U.S. just confirmed its first confirmed case of the Omicron variant in California. Although health experts have warned about the potential of a new variant for months, it’s still a disappointing development. Many people were hoping that the worst of the pandemic was behind them.

These new restrictions arrive on the heels of the U.S. finally re-opening its borders to vaccinated international travels in November. However, it remains unclear the full effect the variant will have on holiday travel plans.

Many people argue that travel bans are mostly ineffective — studies do show that a travel ban can slow the spread of the virus. But it does little to prevent the disease from crossing country borders.

That’s probably why the International Air Transport Association (IATA) warned that these types of restrictions are “not a long-term solution” when it comes to dealing with coronavirus variants.

Ultimately, it’s too soon to tell how long these restrictions will last and how they will impact holiday travel. There’s still a lot that health officials don’t know about the variant and whether people will be comfortable traveling.