The ground delay, which is separate from the outage, is related to "low ceilings" for departures, tied to poor weather conditions.

One of the region's busiest ports has come under scrutiny since revelations that its tower has lost contact with several planes in recent months.

The blackout included losing radar for about 90 seconds at Newark Terminal Radar Approach Control at 3:55 a.m. local time, a source with knowledge of the incident tells CNN.