Hundreds of flights have been cancelled and delayed at Newark Liberty International Airport on Monday due to a staffing issue, authorities said, and the issues persisted into the evening.

As of 10:30 p.m., there were 329 delays and 148 cancellations, according to Flight Aware.

Arrivals to the airport have been delayed for an average of just over four hours, the FAA said.

Staffing issues at Philadelphia Terminal Radar Approach Control, a regional center which guides planes into Newark airport, are the cause of the issues, the FAA said.

The problem began around 1:30 p.m. At that time, the agency said it was slowing arrivals and departures at the airport because of telecommunications and equipment issues at Philadelphia Terminal Radar Approach Control.

Those issues were resolved Monday evening but the staffing issues were ongoing.

The FAA did not respond to an email seeking clarification about the staffing issue or for updates on how long the problems were expected to last, including any impact on Tuesday.

A tweet from Newark Airport’s official Twitter/X account around 8 p.m. said that residual delays were still happening.

United Airlines said in a statement on Monday evening that the airline expected cancellations throughout the evening.

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Chris Sheldon may be reached at [email protected].