“I think the risk of a collision or an incident was increased, but not significantly because of the redundancy in the aviation system,” said Jeff Guzzetti, a former accident investigator for the FAA and the National Transportation Safety Board.

Crashes like January’s deadly collision between a passenger jet and an Army helicopter usually have different causes — a combination of many things that go wrong, he says.

Here’s a look at what happened in Newark — and how key pieces of the safety net protected planeloads of people.

What failed?

The radar and communications systems that a terminal control team in Philadelphia relies on to direct planes in and out of Newark International Airport simultaneously failed twice in the past month for brief periods. The main line that carries the radar signal from another FAA facility in New York failed, and the backup line didn’t work immediately. The system relies in part on aging copper wires and even when there are fiber optic lines, the signal has to be slowed down when it reaches the facility because the FAA computers are so old they can’t handle all the data at full speed.

As a result, the controllers were suddenly unable to see or communicate with planes coming from or going to Newark for as long as 90 seconds on April 28 and May 9. Their radar screens showing each flights in motion suddenly went black. Their radio connections went silent.

The main line failed a third time May 11, but the backup system worked and the radar stayed online. The FAA said a fourth outage Monday knocked out radio communications for two seconds, but the radar stayed online.

After the initial outage, the already shorthanded control center in Philadelphia lost five to seven controllers to trauma leave. Newark’s terminal control team could no longer manage a full schedule of handoffs with the airport’s control tower, leading to hundreds of flight cancellations and delays that rippled across the nation’s airlines. The FAA then imposed safety limits, allowing no more than 28 arrivals and 28 departures every hour. Before, 38 or 39 flights typically took off and landed hourly.

What backup systems does the FAA have?

When air traffic controllers lose the ability to see or speak to airborne planes, they can try text messaging the pilots via data link systems or try high-powered portable radios. An emergency radio frequency might also be an alternative if main communications are down. Tower controllers have high-powered light guns to send a green or red signal to pilots to let them know if they are clear to land even if they can’t talk to them over the radio.

And the entire air traffic control system is built on an overlapping network of radar sites. So if a terminal control team like the one in Philadelphia loses its communications, a controller in a radar center that normally directs planes at higher altitudes might step in. If some other controller in the area hears a pilot broadcasting on an emergency frequency, they too can relay a message.

During these Philadelphia outages, voice communications came back online first while the radar took another minute to reboot, and controllers were able to hand off planes without having to resort to some of those other options.

In a May 9 recording captured by www.liveATC.net, a controller can be heard saying “FedEx 1989. I’m going to hand you off here. Our scopes just went black again. If you care about this, contact your airline and try to get some pressure for them to fix this stuff.” The pilot acknowledged that and wished the controllers “good luck guys” before switching frequencies.

Acting FAA Administrator Chris Rocheleau has tried to reassure the public that all these backups and limits on the number of flights keep flying safe, despite these problems that have exposed how fragile and outdated some air traffic control systems have become.

“When disruptions occur at any airport because of equipment issues or staffing, the FAA will always ensure safety by slowing down airport arrivals and departures and reducing congestion,” Rocheleau posted on X. “We keep the flying public safe because there are redundancies built throughout the entire system used by pilots, technicians and air traffic controllers.”

What can pilots do if they lose communications?

Every pilot is trained on what to do if they can’t talk to the air traffic controllers, and modern passenger jets have their own backup systems. Airline pilots all regularly get refresher training emphasizing safety.

Capt. Miles Morgan oversees all training for 17,000 United Airlines pilots at a facility in Denver filled with simulators and classrooms. He said losing communications is rare, but it’s something pilots prepare for, as most training focuses on what to do if something goes wrong.

“I’ve been flying for 30 years. I’ve got almost 18,000 hours in United airplanes — jets, and I’ve lost communication one time,” Morgan said. “It really ended up not being that big of a deal. I just went to the emergency frequency, got a different channel, and contacted a different facility to get back into communication.”

In addition to multiple communications systems, planes are equipped with collision avoidance technology that shows pilots where all the other planes are moving around them. These systems alert pilots to an approaching aircraft’s trajectory and can recommend evasive action to prevent a collision if planes get too close, Morgan said.

Allied Pilots Association union spokesman Capt. Dennis Tajer said that when pilots lose contact with controllers, their first action is to continue on their last-directed path. If the outage continues, they’ll broadcast their position to every other plane in the area — much like pilots do at small airports that don’t have a control tower — as they follow their flight plans.

“It’s not to downplay the seriousness of communication failure or radar outages, but it’s to recognize that we have procedures, we trained to those procedures, and we have additional equipment that can only enhance the safety margin while we deal with that scenario,” Tajer said.