U.S. Transportation Secretary Sean Duffy warned Sunday about upcoming air travel issues. These issues will worsen before the holidays. This comes as the country entered the third day of federally mandated flight reductions.

“It’s only going to get worse,” Duffy told Jake Tapper on CNN’s “State of the Union. “I look to the two weeks before Thanksgiving. You’re going to see air travel be reduced to a trickle.”

Duffy added that a significant number of people will miss celebrating the holidays with their families. This is due to travel delays caused by Federal Aviation Administration-mandated flight cancellations. These cancellations occurred at 40 high-traffic airports and went into effect on Friday.

The cuts come as the FAA deals with shortages of air traffic controllers amid the dragging government shutdown. As essential workers, air traffic controllers must work during a government shutdown, even without pay.

More than 4,200 flights had been delayed and 1,520 canceled as of Sunday morning, in part because of the mandate. Duffy said there were 81 “staffing triggers” throughout the national airspace on Saturday. This means operations were modified due to staffing shortages. He noted that “18 of 22 controllers in Atlanta didn’t show up.

The FAA-mandated flight cancellations mean a 4% reduction in flight capacity this weekend. It will ramp up to 6% by Tuesday, 8% by Thursday and up to 10% by Friday.

Despite the decrease in air traffic, Duffy said Sunday that travel remains safe during the shutdown.

“We’re working overtime to make sure that it is safe to travel,” he said. “If we have staffing triggers in locations in the American airspace, what we will do is, we will slow traffic. It means you will have delays, and then airlines might cancel flights.”

Duffy expressed concern about what lies ahead. He stated that voting to reopen the government is the “best approach to get America back operational.”

“Next Friday, it’s going to be at 10% to reduce the pressure on controllers,” he said.

“I try to reduce the pressure by lowering flights. But, more controllers keep not coming to work,” Duffy added. “And so the pressure goes back up again.”

The government-mandated flight cancellations entered their third day on Nov. 9. Travelers are once again glued to their phones and computers. They are checking to see whether their flights are among the growing number of cuts.

More than 1,100 flights had already been canceled for Sunday by mid-afternoon, FlightAware data says. This follows more than 1,000 cancellations on Saturday.