At times Monday evening, as few as three air traffic controllers per hour were lined up to monitor via radar the planes flying into and out of the airport, the Federal Aviation Administration said.

Several times over the last year, Newark controllers lost radar or radio service, leaving them unable to talk with planes they were tracking.

The latest incident highlights the air-traffic-control network's aging infrastructure and comes a day after Transportation Secretary Sean Duffy proposed spending billions of dollars to fix it over the next three to four years.

United Airlines Holdings Inc. expects flight reductions at Newark airport to linger through summer and into fall as the crucial travel hub struggles to recover from air traffic control glitches that have already disrupted hundreds of flights.