Amidst an ongoing government shutdown that has persisted for over a month, U.S. airports continue grappling with flight delays, exacerbated by a shortage of air traffic controllers. On Sunday, Newark Airport in New Jersey bore the brunt, with passengers facing delays ranging from two to three hours.

New York City’s Emergency Management office took to social media platform X to warn travelers about the potential ripple effect these delays at Newark could have on the region’s other major airports. They advised those flying to, from, or through New York to brace for schedule adjustments, gate holds, and possibly missed connections. The office urged travelers to verify their flight status before making their way to the airport, suggesting that longer wait times were likely.

Elsewhere, George Bush Intercontinental Airport in Houston, Dallas Fort Worth International Airport, and Chicago O’Hare also reported several delays and a handful of cancellations. This trend was echoed in other major airports, including those in San Francisco, Los Angeles, Denver, and Miami, as reported by FlightAware.

By Sunday evening, FlightAware recorded a total of 4,295 delays and 557 cancellations involving flights within, into, or out of the U.S., though not all were attributed to the shortage of air traffic controllers. For context, in July, prior to the shutdown, about 69% of flights were on time, with 2.5% facing cancellations.

As of Sunday evening, FlightAware said there were 4,295 delays and 557 cancelations of flights within, into or out of the U.S., not all related to controller shortages. In July, before the shutdown, about 69% of flights were on time and 2.5% were canceled.

U.S. Transportation Secretary Sean Duffy has been warning that travelers will start to see more flight disruptions the longer controllers go without a paycheck.

“We work overtime to make sure the system is safe. And we will slow traffic down, you’ll see delays, we’ll have flights canceled to make sure the system is safe,” Duffy said Sunday on CBS’S “Face the Nation with Margaret Brennan.”

He also said he does not plan to fire air traffic controllers who don’t show up for work.

“Again when they’re making decisions to feed their families, I’m not going to fire air traffic controllers,” Duffy said. “They need support, they need money, they need a paycheck. They don’t need to be fired.”

Earlier in October, Duffy had warned air traffic controllers who had called in sick instead of working without a paycheck during the shutdown risked being fired. Even a small number of controllers not showing up for work is causing problems because the FAA has a critical shortage of them.

The Federal Aviation Administration said Friday on X that nearly 13,000 air traffic controllers have been working without pay for weeks.

Staffing shortages can occur both in regional control centers that manage multiple airports and in individual airport towers, but they don’t always lead to flight disruptions. According to aviation analytics firm Cirium, flight data showed strong on-time performance at most major U.S. airports for the month of October despite isolated staffing problems throughout the month.

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