Newark, New Jersey - US authorities said the overstretched airport of Newark, one of three serving the New York metropolitan area, suffered a new 90-second outage early on Friday.

Delays and flight cancellations had already followed an April 28 incident at Newark Liberty International Airport, in which traffic controllers stationed in nearby Philadelphia were unable to communicate with planes.

In the latest incident, according to the Federal Aviation Administration (FAA), there "was a telecommunications outage that impacted communications and radar display" at the same Philadelphia traffic control station that guides aircraft in and out of Newark's airspace.

The outage occurred around 03:55 AM ET on Friday and "lasted approximately 90 seconds," a short statement said.

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Following the first incident, the FAA said Wednesday it was slowing arrivals and departures at Newark, which is one of the US' busiest airports.

Employees involved in the April outage had described a terrifying scene, with four air traffic workers taking short-term, trauma-related leave following the outage, according to a report in the Wall Street Journal.

The new episode will heap additional attention on the US Air Traffic Control system, which has been chronically understaffed and long beset with older equipment due to shortfalls in congressional funding.

In a statement Wednesday, the FAA said it was adding new telecommunications capacity, replacing copper connections with updated materials and deploying backup equipment.

It also cited runway construction as a cause for the slowdown.

The troubles at Newark follow a January 29 mid-air collision near Washington's Reagan National Airport involving a passenger jet and a military helicopter, the first major US commercial crash since 2009.

The FAA has experienced staff cuts due to the Trump administration's reorganization led by Tesla boss Elon Musk's so-called Department of Government Efficiency.

The job cuts do not affect safety employees, and no air traffic control staff have been reduced due to Musk's initiatives, according to the FAA.