Passengers wait in line at a security checkpoint at Miami International Airport on Friday, the eve of the three-day holiday weekend which is likely to see bigger airport crowds.

America’s busiest airport, Atlanta’s Hartsfield-Jackson International, is a blur of activity on the best of days. But an extra layer of anxiety gripped the airport Friday, the eve of a three-day holiday weekend. The partial government shutdown — the longest ever — has thinned the ranks of federal workers who staff airport security lines.

The scene at most of the nation’s airports has so far been marked more by concerned passengers showing up early than by missed flights. Longer lines are evident at some airports, but delays resulting from a rise in federal security screeners calling in sick have been slight.

Yet concern is growing. President Donald Trump and Democrats in Congress remain far apart over Trump’s insistence on funding for a wall along the Mexican border as the price of reopening the government. With the two sides trading taunts and avoiding talks, travel industry analysts and economists are calculating the potential damage if the shutdown drags into February or beyond.

Airlines and hotels would suffer. So would parks and restaurants that cater to travelers. And, eventually, the broader U.S. economy, already absorbing a trade war with China and a global economic slowdown, would endure another blow.

The travel and tourism industries generate about $1.6 trillion in U.S. economic activity — one-twelfth of the economy — and one in 20 jobs, according to the Commerce Department. Macroeconomic Advisers says it expects the economy to expand at just a 1.4 percent annual rate in the first three months of this year, down from its previous forecast of 1.6 percent, because of reduced government spending during the shutdown.

With Martin Luther King Jr. Day on Monday, a federal holiday, the Transportation Security Administration predicts it will screen more than 8 million passengers between Friday and Monday, up 10.8 percent from last year’s MLK weekend. And it will do so with fewer screeners. On Thursday, the TSA said 6.4 percent of screeners missed work, nearly double the 3.8 percent rate the same day in 2018.

A TSA spokesman said the agency was offering overtime to screeners for this weekend, though those workers wouldn’t be paid for their regular pay or for overtime until the shutdown eventually ends.

On top of potentially longer airport security lines this weekend, a blast of winter weather could snarl travel this weekend in the Midwest and Northeast.

Hartsfield-Jackson Atlanta International, home to Delta Air Lines, has likely been the hardest hit airport. Delta said this week that the shutdown will cost it $25 million in January because fewer federal employees and contractors will be flying. By contrast, United Airlines, which has a substantial presence around Washington, D.C., said it hasn’t felt much impact yet.

Some in the airline industry and even in Congress have suggested that longer TSA security lines could exert enough pressure on politicians to break the stalemate that is keeping the government shuttered.

Others have all but lost hope.

“I would love to think that politicians understand that travel and tourism is an incredibly important gear in the economy,” said Ninan Chacko, CEO of Travel Leaders Group, which owns and manages travel agencies, “but I don’t think that is really the rational discussion that is taking place in Washington.”