On a recent afternoon in Philadelphia, an air traffic controller began shouting that he had lost his radar feed for planes flying in and out of Newark Liberty International Airport.
Some of his colleagues still had radar but their radios went dead, prompting frantic calls to their counterparts in New York urging them to keep their planes away from Newark’s airspace.
Then, for 30 harrowing seconds until the radios came back, there was nothing more to do but hope — as they had no means of telling pilots how to avoid crashing their planes into one another.
Shortly after that, one controller discovered a trainee, who had been directing Newark traffic under supervision just moments earlier, shaking in the hallway.
That was the chaotic scene on Monday, April 28, according to several people who were present when controllers working the airspace for Newark lost the means to do their jobs.
The failure of the system the controllers rely on left several of those on duty that day with extreme anxiety, requiring a mental health respite that has caused low staffing levels for days since. It has also prompted more than 1,000 flights at one of the nation’s busiest airports to be canceled or delayed, leaving some passengers feeling frustrated and abandoned.
The struggles with staffing are ironic because the Federal Aviation Administration’s decision to relocate some of Newark’s air traffic control operations to Philadelphia last summer was intended to increase head count.
The nation’s air traffic control system has been plagued by years of dysfunction. The controller ranks were depleted by retirements and a cessation in training during the pandemic. Since then, recruiting and certifying new controllers has been difficult. Existing controllers have been fatigued and even sickened by intense stress and long hours, The New York Times has reported. Some have avoided seeking medical attention because doing so could jeopardize the health care clearances they need to do the work. Turnover is frequent, especially amid illnesses, family turmoil or safety scares.
The outage and its aftereffects at Newark have prompted public outrage.
Transportation Secretary Sean Duffy, who oversees the F.A.A., has called for “a brand-new air traffic control system.” Senator Chuck Schumer of New York, the minority leader, has said the F.A.A. “is really a mess.” Scott Kirby, the chief executive of United Airlines, which is Newark’s biggest user, said the airport “cannot handle the number of planes that are scheduled to operate there” and blamed controllers who “walked off the job.”
But current and former controllers, who requested anonymity for fear of retaliation, and people who witnessed last week’s outages said the controllers’ time away from their duties was appropriate under the circumstances, given the hardship of working under such duress. They also described the unnerving incident as the culmination of nine months of technical glitches that have eroded the Newark team’s confidence in the reliability of the tools that are essential to doing its work.
Last August, in an incident that was later blamed partly on a third-party technician who accidentally cut a data feed from a remote location, a controller lost radar for about 90 seconds, according to people who were there. A week later, radar scopes froze several times, according to F.A.A. activity logs that were reviewed by The Times. Then, about eight months later, the April 28 outages, which lawmakers have blamed on a “fried” copper wire, occurred.
“From what we can gather right now, the communication lines that feed the Newark sector, which resides in Philadelphia, are failing,” Dave Spero, the president of Professional Aviation Safety Specialists, a union that represents airway transportation systems technicians, said in an interview. He said contractors, not the F.A.A. itself, were responsible for those lines.
The F.A.A. said it was working closely with facility managers and vendors to address telecommunication issues across the national airspace system, particularly in the Northeast. Mr. Duffy said the F.A.A. had “slowed down the system” to ensure traveler safety at Newark.
The F.A.A. has acknowledged that some Newark controllers have taken time off to deal with the stress of the recent outages. On Tuesday, the agency said it had slowed arrivals and departures at Newark, in part because of staffing shortages. It added that it was “taking immediate steps to improve the reliability of operations” at the airport, including installing new, high-bandwidth data connections, deploying a backup system to Philadelphia and increasing staffing among the Newark controller ranks.
Mr. Duffy is expected on Thursday to announce additional details of a planned air traffic control overhaul, which he has been working on since a midair collision near Ronald Reagan National Airport outside Washington this year killed 67 people.
The F.A.A. said in a statement that it had 22 certified Newark controllers in Philadelphia and almost as many in training.
But that is not the whole picture. Because of mental health leave and other personnel matters, only 16 certified controllers are currently available to call on each day, according to people familiar with the situation, and more than double that number would typically be needed to cover all the shifts.
Aviation experts say — and the F.A.A. acknowledges — that there are no quick fixes to controller shortages.
Being a controller for a busy airspace like Newark’s typically requires years of nuts-and-bolts training and experience in other busy airspaces close to major cities.
Even a veteran controller who joined the Newark team from a hub like Atlanta or San Diego would need up to a year of specialized training to become familiar with the nuances of Newark’s traffic — which typically involves 80 or more departures and landings in a given hour — according to controllers with knowledge of that airspace. In addition to that, Newark controllers handle the traffic at smaller regional airports, including Teterboro, N.J.
Controllers working the Newark airspace from Philadelphia were supposed to be the solution, rather than the problem. The F.A.A. reasoned that the relatively low cost of living near Philadelphia would attract more workers who wanted to purchase homes or raise families, and that the Philadelphia International Airport control tower where they would be stationed was newly renovated.
The move was fraught from its inception. Some controllers resisted leaving their perch in Westbury, N.Y., where they had worked alongside colleagues handling flights in and out of LaGuardia Airport and Kennedy International Airport for years or even decades.
Some controllers who argued to the F.A.A. that the relocation would place undue hardship on their families were permitted to stay in Westbury. Others opted to take their chances in Philadelphia, collecting a $100,000 incentive payment for doing so. Their workstations in the new building, which the F.A.A. had spent $36 million to modernize, were fitted with real-time tracking technology.
They reported to their new posts on July 28.
The controllers for Newark initially worked on a reduced flight schedule to smooth out any kinks. But by mid-August, with summer travel robust, standard traffic levels in and out of Newark had resumed, and flights were proceeding normally.
Then on Aug. 27, a Newark controller in Philadelphia lost radar imagery for roughly a minute and a half after the technician’s mistake, according to two people who were in the control hub that day.
The controller was monitoring half a dozen planes at the moment the radar vanished, including two United Airlines jets, one of the people recalled. With no visual imagery to guide him, he tried to direct the pilots from memory, according to three people with knowledge of the incident.
“Attention all aircraft. Radar contact is lost. Radar contact is lost,” the controller said, according to an audio recording of the event.
By the time radar imagery returned, said two people with knowledge of the incident, one of the flights was well into LaGuardia’s airspace and was flying over the Hudson River.
The controller, who had decades of experience, retired within days of the incident, said the three people with knowledge of the matter.
The trouble in Philadelphia persisted. Less than a week later, Labor Day travelers flying in and out of Newark faced delays and a ground stop — a temporary halt to takeoffs and landings — because of unrelated radar equipment problems, according to the F.A.A. The agency blamed “data transmission issues” in the regional system.
Those were an outgrowth of the way the F.A.A. handled the transfer of Newark flight data to Philadelphia when it moved the controllers, according to government and union officials at the time. Rather than feeding flight data that was generated at Newark straight to Philadelphia, the F.A.A. instead routed the data initially to Westbury, and then to Philadelphia from there, those officials said.
That meant that the data had to travel further and was also vulnerable to being overloaded at times by other hubs in the system that were experiencing glitches, said Mr. Spero, the president of the safety specialists’ union.
“It caused what they call a cascade failure with target freezing,” Mr. Spero said. He was referring to the dots that represent moving aircraft on radar screens that, according to F.A.A. logs of that day, froze in several places, prompting an alert.
The F.A.A. said in a statement that it was establishing a communication system that will not require the Philadelphia facility to rely on a feed from New York.
Controllers said last fall that while data and capacity hitches had not been their chief objection to relocating, they had long been a source of anxiety. It has only gotten worse as the isolated glitches have come to seem like more of a trend, said the people who witnessed the recent events in Philadelphia.
One controller who was there on April 28 made it to his car before breaking into tears, one of those people said. He has taken time off, this person added, and will need to be cleared by a mental health professional before he can return.
Mark Walker contributed reporting.