The Transportation Security Administration plans to begin closing a handful of security checkpoints at airports around the U.S. as soon as this weekend in response to staff shortages triggered by a partial federal government shutdown now in its third week.

Miami International Airport expects to shut one of its concourses for several days starting Saturday afternoon and will move flights to other gates, according to a statement by the airport.

Separately, a union representing more than 10,000 air-traffic controllers filed suit in federal court in Washington on Friday, charging that it’s illegal to force them and other aviation employees to work without compensation.

More than 51,000 TSA employees have also been on the job without pay since Dec. 22 and missed their first paycheck on Friday. On Thursday, the agency saw a 55 percent increase in employees calling in sick, from 3.3 percent a year ago to 5.1 percent, spokesman Michael Bilello said in an email.

Bilello said on Twitter that the TSA is working with “stakeholders and industry partners to explore efforts to consolidate officers and operations.”

Concourse G at the Miami airport will be closed after 1 p.m. Saturday through Monday and travelers will be directed to other checkpoints.

United Continental Holdings operates some flights at that concourse. “We will work to ensure we do everything we can for our customers and we do not expect any operational impact,” said Frank Benenati, a United spokesman.

TSA hasn’t heard of any other airport planning to shut an entire concourse like the one in Miami, Bilello said. It’s routine for TSA to open and close screening lanes as volume at airports rises and falls.

Airport security officers, along with air traffic controllers and employees at more than a dozen U.S. agencies and departments, have been caught in a political battle between President Donald Trump and congressional Democrats over whether to fund a border wall with Mexico.

The security screeners and controllers are among workers declared essential to security and safety and have been ordered to work without pay.

The lawsuit filed by the National Air Traffic Controllers Association union charges that Trump, the Federal Aviation Administration and other U.S. officials are violating workers’ constitutional rights by “depriving them of their hard-earned compensation without the requisite due process.”

In some cases, the lack of pay is having a “devastating effect” on employees, the suit said. One plaintiff, Amanda Fuchs, a controller from Clermont, Florida, is a single mother who also helps care for her brother, mother and stepfather. The shutdown is hurting her ability to keep up with those responsibilities, the suit said.

The FAA declined to comment Friday on the controllers’ lawsuit.

In similar shutdowns Congress and the White House have always agreed to pay back wages to government employees, though some contractors haven’t been paid in arrears. The House on Friday passed legislation that would give federal workers back pay. The Senate already passed the measure, which now goes to Trump for his signature.

Unlike the controllers, TSA officers and other workers deemed essential, most federal employees are furloughed and haven’t been working.

The TSA has vowed to take steps to ensure that screening of people and bags at airports isn’t compromised by the shutdown.

“As the current lapse in funding persists, TSA officers continue to perform with the utmost professionalism and dedication,” Bilello said. “We thank TSA officers for their resilience and diligence, and we thank industry and the public for their continued acts of kindness and support.”

While the percentage of officers calling in sick is up substantially, the overall number of missing screeners remains small and airport operations have had minimal disruptions, according to the agency.

TSA officers screened 1.96 million passengers on Thursday and 99.9 percent waited in line less than 30 minutes, according to the agency.