A government shutdown could disrupt travel with longer lines at the airport, national park closures and snarled itineraries. Nonessential federal operations would cease at midnight on Tuesday if Congress fails to pass legislation to keep the government functioning.

Many airport employees, including air traffic controllers and Transportation Security Administration staff, would be forced to work without pay. The government’s continuing efforts to strengthen the air traffic control system would also be stymied, with some much-needed training and hiring put on ice.

Though transportation systems, including air and rail, would continue to operate, a shutdown could bring financial losses of up to $1 billion each week for the country’s travel economy and heighten “uncertainty in our travel system,” said Geoff Freeman, the president and chief executive of the U.S. Travel Association, a trade group that promotes travel to and within the country.

“The longer a shutdown drags on, the more likely we are to see longer T.S.A. lines, flight delays and cancellations, national parks in disrepair and unnecessary delays in modernizing travel infrastructure,” Mr. Freeman said in a statement.

Here is a rundown of the expected impact of a government shutdown on the travel sector.

Air Travel

A shutdown would likely mean long security lines at airports and numerous delayed flights. The vast majority of the 61,000 T.S.A. workers and more than 13,000 air traffic controllers would work without pay, according to the Transportation Department.

That was what happened during the longest and most recent shutdown, from December 2018 to January 2019, leading to many T.S.A. agents calling out sick at higher than usual rates. The increase in absences resulted in shuttered security checkpoints — and, in Miami, even the temporary closure of an entire terminal.

Amtrak

Though it receives public funding, Amtrak operates as an independent company and will continue normal operations during a government shutdown.

“Passengers planning to travel on Amtrak trains in the Northeast Corridor and across the country in the coming days and weeks can be assured that Amtrak will remain open for business,” W. Kyle Anderson, an Amtrak spokesman, said in a statement.

National Parks

Most National Park Service sites will be “closed completely to public access” during a government shutdown, according to the service’s contingency plan.

“Areas that by their nature are physically accessible to the public will face significantly reduced visitor services,” according to the plan, which was published in March 2024. It adds that the public will be asked not to visit national parks for the duration of a shutdown.

Rachel Pawlitz, a park service spokeswoman, said plans for a shutdown were “being reviewed and updated” but declined to elaborate.

On Friday, more than 35 former park superintendents wrote a letter to the Trump administration urging the closure of national parks if the government shuts down, citing damage that occurred during the 2019 shutdown, when parks were left open with limited staff.

A shutdown would be the latest in a series of blows to the National Park Service, which has lost at least 24 percent of its permanent staff since January, according to the National Parks Conservation Association. Nearly one million park visitors would be turned away every day if the government shuts down, and communities surrounding the parks could lose as much as $77 million each day parks are closed, according to the association.

State, local or tribal governments can pay to keep their national park sites open with the N.P.S. director’s approval. Arizona, Colorado and Utah committed to keeping national parks within their borders open ahead of a funding deadline in 2023, though a shutdown was ultimately avoided.

Travelers should use Recreation.gov for specific information on campsite reservations, guided tours and other visitor services.

Museums

The last time a government shutdown looked imminent, in December, the Smithsonian Institution said it would continue operations for several days before closing its museums, research centers and the National Zoo. (A shutdown did not ultimately occur.)

The Smithsonian, which receives about 62 percent of its funding from the federal government, oversees 21 museums and other sites around Washington and two museums in New York. Representatives for the Smithsonian did not respond to multiple requests for comment on the institution’s plans for a potential shutdown.

Open-air monuments in Washington, including the National Mall, will remain accessible, though facilities such as restrooms and information kiosks may be closed.

Passports

Visa and passport processing would not be immediately affected. The federal agencies involved — the U.S. Citizenship and Immigration Services and the State Department’s Bureau of Consular Affairs — are funded by passport fees and don’t depend on congressional appropriations for most programs.

However, the American Immigration Lawyers Association said that consular operations could be disrupted if fee-generated funds ran out.

“In such a case, posts will generally only handle diplomatic visas and ‘life or death’ emergencies,” the group said on a general information page on its website.

Borders

The country’s entry ports — sea, land and air — will stay open, and most immigration, border and customs agents will continue to work, according to the Department of Homeland Security. U.S. Immigration and Customs Enforcement operations can generally continue, the American Immigration Lawyers Association said. Most of ICE’s roughly 20,000 employees are considered essential and would work during a shutdown.

In past government shutdowns, international travelers with valid visas and passports were not affected.

Follow New York Times Travel on Instagram and sign up for our Travel Dispatch newsletter to get expert tips on traveling smarter and inspiration for your next vacation. Dreaming up a future getaway or just armchair traveling? Check out our 52 Places to Go in 2025.