Flying into or out of Newark Liberty International Airport has brought plenty of misery in the last week, with cancellations, delays stretching well past five hours and flight diversions that have stranded travelers far from their destinations.

Passengers are reporting on social media that they have missed flights and spent hours stuck on the tarmac aboard planes. Some are still struggling to make new travel arrangements.

The disruptions, which stretched into Friday with delays averaging over two hours, have highlighted ongoing air traffic control staffing issues. The troubles prompted United Airlines, Newark’s largest carrier, to cut nearly three dozen round-trip flights per day at the hub beginning this weekend, the carrier’s chief executive, Scott Kirby, announced on Friday.

Here’s what anyone heading to Newark Airport needs to know.

Air traffic control staffing is limiting capacity

Last summer, management of the airspace surrounding Newark shifted from New York to Philadelphia. This move, which involved relocating at least a dozen air traffic controllers, was meant to ease air traffic delays.

The Federal Aviation Administration has attributed this week’s flight disruptions at Newark to equipment failures and unspecified staffing issues at the Philadelphia air traffic control center as well as to construction on one of Newark’s runways.

These ongoing staffing issues are “effectively limiting the capacity of Newark Airport,” said Aidan O’Donnell, the general manager of New Jersey airports at the Port Authority of New York and New Jersey.

The other major New York City airports, Kennedy and LaGuardia, are managed by the New York control center.

One of Newark’s runways is closed

One of the airport’s three runways was shut down on April 15 for rehabilitation and repaving, with plans to reopen in mid-June.

This is a “very routine construction project,” said Mr. O’Donnell, and the airport had prepared for it extensively by taking steps such as scheduling fewer flights during this period.

Though the airport has two remaining open runways, the F.A.A. has underutilized one of them during the closure, Mr. O’Donnell said. “When we only have one runway that’s available, we are simultaneously landing and departing on the same runway, which is the least efficient way that traffic can be managed into and out of Newark,” he added.

The airport has more than 1,000 scheduled arrivals and departures each day, the majority of which are operated by United.

The wave of disruptions that started on Monday has only intensified

The Philadelphia control center experienced telecommunications and equipment issues on Monday, an F.A.A. spokesperson said. That led to hundreds of delays and cancellations and three dozen flight diversions that day, Mr. O’Donnell said. He added that for two hours on Monday afternoon, no flights departed from or landed at Newark.

The disruptions continued through the week as air traffic controller shortages worsened in Philadelphia. Scott Kirby, the chief executive of United Airlines, said in a letter to customers that more than 20 percent of the air traffic controllers responsible for Newark “walked off the job” this week.

Mr. Kirby added that staffing shortages at the Philadelphia control center have been a problem for years.

A spokesman for the National Air Traffic Controllers Association declined to comment.

The problems may persist for weeks or months

The next few weeks could be challenging, Mr. O’Donnell warned.

Mass flight delays and cancellations can take days to resolve, as airlines navigate getting passengers, crew and aircraft back on track. Both United and JetBlue Airways have issued flight waivers allowing travelers to rebook without incurring extra fees.

United will cut 35 out of an average of 328 round-trip flights per day from its Newark schedule starting this weekend. The airport, one of the airline’s seven hubs, is a key gateway for flying to Europe, India and the Middle East.

Without enough controllers, “Newark airport cannot handle the number of planes that are scheduled to operate there in the weeks and months ahead,” Mr. Kirby said, adding that the flight reduction was a stopgap measure “since there is no way to resolve the near-term structural F.A.A. staffing issues.”

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