As the nation grapples with ongoing air traffic control staffing shortages, travelers faced another round of delays on Friday. This disruption comes as the government shutdown, which started on October 1, looms ever closer to the one-month mark.

U.S. Transportation Secretary Sean Duffy has been vocal about the mounting challenges, cautioning that passengers will likely encounter increasing flight delays and cancellations. The reason? Air traffic controllers continue to perform their critical duties without pay due to the shutdown.

“Each day brings new challenges,” Duffy remarked to reporters on Thursday, following a private meeting at the White House. The session, which included Vice President JD Vance and key figures from the aviation industry, focused on the shutdown’s repercussions on the U.S. travel infrastructure.

The Federal Aviation Administration reported numerous staffing-related delays on Friday, impacting airports in cities such as Boston, New York City, Nashville, Houston, Dallas, and Newark, New Jersey. Particularly hard hit were Boston, Nashville, and New York City, where passengers experienced delays averaging over two hours.

Adding to the concern, aviation analytics firm Cirium noted a “broader slowdown” across the U.S. aviation network on Thursday. This marks the first significant indication since the onset of the shutdown that staffing-related disruptions are becoming more widespread.

On Thursday, many major U.S. airports reported below-average on-time performance, with fewer flights departing within 15 minutes of their scheduled departure times, according to Cirium. The data does not distinguish between the different causes of delays, such as staffing shortages or bad weather.

Staffing-related delays at Orlando’s airport on Thursday, for example, averaged nearly four and a half hours for some time, according to the FAA.

Most controllers are continuing to work mandatory overtime six days a week during the shutdown without pay, the National Air Traffic Controllers Association has said. That leaves little time for a side job to help cover bills, mortgage and other expenses unless controllers call out.

Duffy said controllers are also struggling to get to work because they can’t afford to fill up their cars with gas. Controllers missed their first full paycheck on Tuesday.

“For this nation’s air traffic controllers, missing just one paycheck can be a significant hardship, as it is for all working Americans. Asking them to go without a full month’s pay or more is simply not sustainable,” Nick Daniels, president of NATCA, said Friday in a statement.

Last weekend, a shortage of controllers led to the FAA issuing a brief ground stop at Los Angeles International Airport, one of the busiest in the world. Flights were held at their originating airports for about two hours Sunday until the FAA lifted the ground stop.

Some U.S. airports have stepped in to provide food donations and other support for federal aviation employees working without pay, including controllers and Transportation Security Administration agents.

Before the shutdown, the FAA was already dealing with a shortage of about 3,000 air traffic controllers.