A commercial airliner takes off past the air traffic control tower at San Diego International Airport during the first day of a partial U.S. government shutdown in San Diego, California, U.S., October 1, 2025. REUTERS/Mike Blake

By Doyinsola Oladipo and David Shepardson

NEWARK/WASHINGTON (Reuters) -The number of air traffic controllers calling in sick since the government shutdown began last week has seen a slight "tick up", U.S. Transportation Secretary Sean Duffy said on Monday, cutting air traffic staffing by 50% in some areas at times, though he did not specify where the staffing issues were occurring.

Air traffic controllers and Transportation Security Administration officers must still turn up for work during the shutdown, but are not being paid.

Duffy said there had been a "slight tick up in sick calls" in certain areas, noting that in some areas there was a 50% reduction in air traffic staffing on certain days, without indicating which airports were affected or for how long.

"You'll see delays that come from that... if we have additional sick calls, we will reduce the flow consistent with a rate that's safe for the American people," Duffy said.

He said controllers are set to miss their first paycheck on Oct. 14.

Duffy and the president of the National Air Traffic Controllers Association spoke at a press conference at Newark Liberty International Airport to discuss the effects of the shutdown. The airport, one of three giant facilities that service New York City, is a major United Airlines hub.

The union representing more than 13,000 U.S. air traffic controllers urged workers to remain on the job during the ongoing partial government shutdown that requires them to work without pay.

President Donald Trump has made transportation a focal point in a government shutdown battle with the Democrats, cutting off more than $28 billion of aid for climate programs, subways, tunnels and mass transit in Democratic-leaning states like New York and Illinois.

Last week Vice President JD Vance pulled air travelers into the shutdown debate when he said they "may not arrive on time because the TSA and the air traffic controllers are not getting paid today," on Fox News. No flights are believed to have been delayed because of the shutdown.

In 2019, during a 35-day shutdown, the number of absences by controllers and Transportation Security Administration officers rose as workers missed paychecks, extending checkpoint wait times at some airports. Authorities were forced to slow air traffic in New York, which put pressure on lawmakers to quickly end the standoff.

(Reporting by David Shepardson; Editing by Bill Berkrot and Chris Reese)