Newark Liberty International Airport’s chaotic weekend continued into Monday when hundreds of flights were delayed or canceled.

Bad weather and a lack of air traffic controllers have led to widespread delays and cancellations at New Jersey’s largest airport. The staffing shortage at the Federal Aviation Administration is not a new problem, but industry experts contend it’s become worse since Newark’s air traffic controllers were moved by the FAA from Long Island to Philadelphia last summer.

“Moving these controllers to the Philadelphia TRACON Center is, long-term, going to be good, if the FAA is able to manage this well, and that’s a big if,” said Henry Harteveldt, an airline industry analyst for Atmosphere Research Group.

In response to the mounting delays, United is canceling around 35 flights per day at Newark Airport. United CEO Scott Kirby said in a statement: “It’s disappointing to make further cuts to an already reduced schedule at Newark, but since there is no way to resolve the near-term structural FAA staffing issues, we feel like there is no other choice in order to protect our customers.”

Kirby also accused air traffic controllers of walking off the job last week in Philadelphia, a claim denied by NATCA, the union representing these workers. As part of a statement, the union said air traffic controllers “temporarily lost radar and communications with the aircraft under their control, unable to see, hear, or talk to them. The controllers did not ‘walk off the job’ as it has been reported by the media. Due to the event, the controllers took absence under the Federal Employees Compensation Act.”