NEW YORK (AP) — Passengers with flights to or from Newark Liberty International Airport encountered long delays and cancellations Saturday due to an air traffic controller shortage, a nationwide problem the Trump administration has pledged to fix.

The busy airport outside New York City experienced disruptions all week. Faulting the Federal Aviation Administration’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 Saturday.

United CEO Scott Kirby said the technology used to manage planes at the New Jersey airport failed more than once in recent days. The flight delays, cancellations and diversions the equipment problems caused were compounded when more than one-fifth of Newark’s traffic controllers “walked off the job,” he said.

“This particular air traffic control facility has been chronically understaffed for years and without these controllers, it’s now clear — and the FAA tells us — that Newark airport cannot handle the number of planes that are scheduled to operate there in the weeks and months ahead,” Kirby wrote in a letter to customers.

Airport status reports from the FAA said staffing issues were causing average delays of nearly two hours and ones as long as five hours for flights scheduled to arrive at Newark on Saturday morning. Departures were delayed by an average of 45 minutes. , and average delays of 45 minutes for departures on Saturday morning, according to the status reports.

By late afternoon, arriving flights were running more than three hours behind schedule, while the delay for departing flights had shortened to a half-hour on average. The “misery map” maintained by flight tracking company FlightAware showed the ripple effect on airports in Los Angeles, Atlanta, Chicago, Miami, Dallas and other cities.

United Airlines operates the most flights out of Newark by far, and 35 flights represents about 10% of the round-trip domestic schedule operated by the carrier and its regional United Express network, according to information on the company’s website.

Newark Liberty International Airport pointed to both staffing issues and “construction” when it warned travelers about delays on Thursday.

The Trump administration says it’s been trying to “supercharge” the air traffic controller workforce and make moves to address the nation’s shortage of controllers. The U.S. transportation secretary, Sean Duffy, on Thursday announced a program to recruit new controllers and give existing ones incentives not to retire.

The National Air Traffic Controllers Association, a workers’ union, said at the time that those moves could help address staffing shortages, but it also said the system is “ long overdue for technology and infrastructure upgrades.”

Duffy said on Friday that he visited with “our hard working air traffic controllers as we work to fix these equipment outages caused by outdated technology.”

United’s decision to pare back its flight schedule in Newark come at an already uncertain time 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 to offer two separate forecasts for how it could perform financially this year: one if there were a recession, and one if not.

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