To maintain safe operations, the agency said it will reduce the flow of air traffic, which can result in flight delays or cancellations.

After 9 p.m. Eastern time, the FAA was reporting staffing-related delays at locations like Dallas Fort Worth International Airport, LaGuardia Airport and Newark Liberty International Airport.

The New York City region appeared to be hit particularly hard. LaGuardia Airport, for example, was experiencing an average delay of more than two hours.

The National Air Traffic Controllers Association union didn’t immediately respond to a request for comment. The labor group’s president, Nick Daniels, earlier Friday backed a “clean” short-term spending bill to reopen the government.

Controllers have a unique degree of leverage in the ongoing funding stalemate. Staffing shortfalls causing delays have attracted widespread media coverage in recent weeks, with the GOP pointing to the issue in its shutdown messaging.

Flight disruptions at key aviation centers after some controllers called out sick have been widely credited with hastening the end of the last prolonged shutdown in early 2019.

NATCA recently said it hasn’t seen a spike in controllers taking sick leave, but it has noticed an uptick in so-called “staffing triggers” from the FAA — cases in which the agency moves to slow air traffic due to worker shortfalls.