Newark, New Jersey - Regulators said Wednesday they have been slowing arrivals and departures at one of the US' busiest airports following a 90-second traffic control system outage last week that has industry experts sounding alarm bells.

Delays and flight cancellations have followed the April 28 incident at Newark Liberty International Airport in the state of New Jersey – one of the three major airports serving the New York metropolitan area.

For about a minute and a half, US air traffic controllers stationed in nearby Philadelphia were unable to communicate with Newark planes as the radios and radar went out, according to accounts in the media.

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

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

In a statement Wednesday, the Federal Aviation Administration said it was slowing arrivals and departures while taking "immediate steps" to improve reliability at Newark.

This includes "accelerating technological and logistical improvements and increasing air traffic controller staffing" at Philadelphia, where Newark's air space is managed.

The agency said it was adding new telecommunications capacity, replacing copper connections with updated materials and deploying backup equipment.

It also cited runway construction as cause for the slowdown.

Transportation Secretary Sean Duffy is set to announce upgrades to the US air traffic control system at a news conference on Thursday.

The effort is part of what the Trump administration says will be a "golden age of transportation," according to a DOT advisory.

The troubles at Newark follow a January 29 crash at Reagan National Airport involving a civilian plane and a military helicopter, the first major US commercial crash since 2009.

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

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

Senate Democratic Leader Chuck Schumer said Tuesday he called for a full investigation into the problems.

"Why have the staffing shortages at Newark and other critical airports been allowed to continue?" Schumer asked. "What role have DOGE cuts played in aggravating the chaos?"