Some arriving flights are being delayed four to seven on average at Newark Liberty International Airport according to FlightView.

United Airlines is seeing most of those delays, as travelers say flying has been extremely stressful over the last week.

U.S. Transportation Secretary Sean Duffy says flying is still safe, but technology is outdated.

In a letter, Gov. Phil Murphy urged Secretary Duffy to prioritize the New Jersey - New York region, the busiest airspace in the nation.

“Decades of underinvestment in the maintenance of critical air traffic control infrastructure, delays in upgrading to modern 21st-century air traffic control technology, and inadequate air traffic control staffing have resulted in a frail system nationwide," Murphy wrote. “We expect millions of additional passengers next year as we prepare to host the World Cup finals and must avoid additional disruptions or strains on the system.”

Duffy is expected to make an announcement next week with a plan for an all-new air traffic control system.

Travelers remain worried about getting to where they need to go now and wish they had some sort of heads-up.

“It's very stressful, and I feel like somebody should be able to communicate earlier or two days before if you know this is going to happen so we would actually have another alternative,” said Mildree Asare, who was traveling to Ohio.

FAA officials said in a statement Monday that controllers who work at the Philadelphia-based facility that coordinates flights to and from Newark had taken time off “to recover from the stress of multiple recent outages.”

“While we cannot quickly replace them due to this highly specialized profession, we continue to train controllers who will eventually be assigned to this busy airspace,” the FAA statement said.

The airport faced disruptions last week as well.

United CEO Scott Kirby said in a letter to customers over the weekend that the technology used to manage planes at the New Jersey airport failed more than once in recent days.

The flight delays, cancellations and diversions that the equipment problems caused were compounded when more than one-fifth of Newark’s traffic controllers “walked off the job,” he said.

Faulting the FAA's alleged failure to address “long-simmering” challenges related to the air-traffic control system, United Airlines cut 35 daily flights from its Newark schedule starting last Saturday.

Messages seeking comment were left with the air traffic controllers labor union and the federal Transportation Department, which oversees the FAA.

United’s decision to pare back its flight schedule in Newark comes at an already uncertain period for U.S. airlines. Potential customers across the industry are reconsidering whether to fly for work or for vacation given all the unknowns about what President Donald Trump’s trade war will do to the economy.

Uncertainty is so high that United recently made the unusual move of offering two separate forecasts for how it could perform financially this year: one if there were a recession and one if not.

United flies to 76 U.S. cities and 81 international destinations from Newark.