A major East Coast airport hub, particularly for United Airlines, has been in the throes of an air-traffic control staffing shortage that has led to cascading delays and cancellations around the country.

As ABC 7 reports, Newark International Airport in Newark, New Jersey has been in chaos for the last week or so, and particularly with United flights, the effects are being felts at SFO as at other major airports around the country. The flight-tracking site Flightview shows that around 30% of departing flights out of SFO were delayed today, and around 20% of arriving flights were late or "very late."

ABC 7 spoke to two travelers whose flight out of Newark to SFO was delayed by seven hours, and even though they were rebooked on a different flight, it meant they missed their connection to Hawaii.

Around 300 flights in and out of Newark were delayed on Tuesday. And this is also happening as the Real ID law takes effect, causing potential TSA delays for passengers who don't have Real IDs yet or passports.

Newark, code EWR, is the New York City hub for United Airlines and its primary hub overall, as well as being an operating base for American and Jetblue. A group of air-traffic controllers at the airport are currently on leave because, as New York Magazine reported this week, they experienced an incident on April 28 in which they lost all radar and radio contact with around 20 inbound planes for around 90 seconds — a situation that could have turned catastrophic very quickly, as it is their job to make sure planes do not crash into each other on approach or landing.

According to a Wall Street Journal report on the incident, radio communication came back first, and the stressed controllers spent the day not knowing if they might lose sight or sound of the aircraft again. "We don’t have a radar, so I don’t know where you are," one controller could be heard telling a United pilot once the radio returned. And another told a private jet, "I want to at least get you towards something and clear of all the other aircraft in case we lose the frequency again."

The cause of the incident was apparently a fried copper wire that was quickly fixed, but the aftermath of the situation is exacerbated by the nationwide shortage of air-traffic controllers, which has been widely reported on in the last few years, and which has led to a scary number of near-miss incidents at airports and some accidents. (This is in part a domino-effect of President Ronald Reagan's union-busting effort of 1981 when he fired all striking air-traffic controllers, leading to a wave of new, young hires in the early 1980s, most of whom recently retired.)

The air-traffic controllers' union said that the group — at least five individuals — at Newark qualified for 45-day trauma leave after the April incident, and the report further said that the control tower was now short 20% of its staff. The 45-day leave suggests that things won't return to normal, staffing-wise, until June 15.

Clint Henderson, who writes for travel site The Points Guy, tells ABC 7, "I'm actually telling people who are at all nervous or risk adverse, not to fly into Newark. Not just because of delays and cancellations, but also just for basic safety reasons."

Related: United Airlines Jet Clips Wing of Another at SFO, Emergency Crews Respond

Photo: David Syphers