Problems at U.S. airports could worsen beyond hours-long security lines and missed flights if Congress does not agree on a way to pay Transportation Security Administration officers. Federal officials have warned that staffing shortages may close some smaller airports to passengers and commercial flights.

While no specific airports have emerged publicly as potential candidates, Transportation Secretary Sean Duffy and the TSA’s acting leaders said they expected more airport screeners to quit or call out of work after Friday, when TSA personnel were set to miss their second full paychecks since mid-February.

They have been required to work without pay since funding for the Department of Homeland Security, which the TSA falls under, lapsed on Feb. 14.

“This level of disruption is unprecedented,” Ha Nguyen McNeill, the agency’s acting administrator, said. “We are being forced to consolidate lanes, and may have to close smaller airports if we do not have enough officers.”

The leader of the labor union that represents TSA officers announced that the agency created a list of about 75 airports that could potentially close to free up officers for major hubs facing long security wait times.

With 11% of officers nationwide missing scheduled shifts recently, the impacts are already being felt in places like Houston and Atlanta, where massive queues have formed. The Biden administration is considering invoking a national emergency to ensure TSA workers are paid, as calls for action intensify amidst the rising crisis.