Duffy says contractor copper-to-fiber work caused the overload
Trump administration officials said at a press briefing Saturday that new technology being added to the nation’s air traffic control system overloaded antiquated equipment, producing “intermittent” communications issues and radar gaps that led to the ground stop.
Duffy said a contractor had been working on replacing a section of the system’s old copper wire with new fiber wire, and that the work somehow resulted in the system overload. He said officials were probing whether contractor “incompetence” or a faulty router was the cause.
“Specifically, we had over 1,000 connection attempts every 4 to 5 seconds,” Duffy said. “And what that did was gave us issues with our communication with airplanes, and it also caused some disruption with our radar feeds. And when we see that, your safety is paramount, we shut down the airspace.”
Planes flying at the time of the ground stop were able to land safely using “well-known procedures” in place for such circumstances, Duffy said Friday.
Federal Aviation Administration Administrator Bryan Bedford told reporters Saturday that intermittent frequency instability affected as many as 17 of the 22 U.S. regional air traffic control centers. “The thing that was unique about this is that it was a type of failure that wasn’t local because it was part of the communication system,” Bedford said. “It propagated around the country.”
The government has been working to overhaul the outdated technology air traffic controllers rely on since Congress approved $12.5 billion for the effort last year. Miles of old copper wires have been replaced with fiber optic lines, and old radio systems are gradually being replaced at airports. The work is far from complete, and Duffy used the news conferences on Friday and Saturday to urge Congress to provide more funding.
How the regional centers work
The FAA grounded flights nationwide Friday due to issues at regional air traffic control centers, an FAA notice said. The United States operates 22 regional air traffic control centers, managed by the FAA, that oversee long-distance aircraft operating between departure and arrival airports, according to Michael McCormick, associate professor and program coordinator in the Department of Applied Aviation Sciences at Embry-Riddle Aeronautical University. McCormick estimates these control centers take over flights at altitudes over 10,000 feet.
These centers, which operate in places such as Anchorage, Alaska, Houston and Indianapolis, are one of the three layers that guide pilots. Airport towers direct pilots at takeoff at the 500-plus airports that have towers. Terminal Radar Approach Control centers then take over as pilots move further from the airport, and the regional centers take over after that. When descending, the reverse happens, experts say.
Controllers at the regional centers sit at radar displays and are responsible for only that airspace. “As you fly, your flight is handed off from one controller to another controller,” said Stephen Creamer, president of the Air Traffic Control Association, a trade group for equipment manufacturers involved with air traffic control. “That handoff process is like taking the screen and the aircraft on one screen and making sure it’s on someone else’s screen before you send the communications over to that next controller and have the pilot start talking to them.”
McCormick said the country’s regional, high-altitude air traffic control centers need to be connected to remote radio transmitter or receiver sites to allow for radio frequency coverage to communicate with aircraft. Those transmitter sites are connected to the centers via telecommunications systems that are in the process of moving from copper wires to fiber optic lines. An aviation expert described the network the regional centers communicate through as “one of the largest telecommunications systems in the country,” and said disruptions like Friday’s hourslong, nationwide grounding can reverberate widely. The two-way communication is important to ensure, among other things, that planes maintain safe spacing, McCormick said.
“What is especially problematic in this case is that it’s what’s known as a rolling outage,” McCormick said. “In other words, it’s unpredictable and it may impact one air traffic control center now and then it gets better and then impacts another air traffic control center.”
McCormick and other aviation experts said the FAA is now transitioning to what’s known as controller pilot data link — a digital, text-based messaging system that allows controllers and pilots to exchange routine clearances, instructions and requests through the data link instead of voice radio.
How a ground problem reaches flights far away
In September, Newark Liberty International Airport temporarily lost radar communications with aircraft after a backup fiber optic line was inadvertently cut by railroad construction workers, forcing the FAA to immediately cancel hundreds of flights going in and out of the airport. Airline experts said that scenario was different from what occurred on Friday.
Andrew Charlton, an aviation consultant, said the “knock-on” effect of Friday’s disruption is incredible. “The aircraft doesn’t just fly from A to B and back to B and then stop,” Charlton said. “It then moves onto C and then over to E and around and around and around. It is, of course, exacerbated if you’re talking about long-haul flights, international flights over the Atlantic or over the Pacific.”
Aviation experts said pilots can still communicate during intermittent communications disruptions, noting that many planes have satellite phone systems. John Hansman, an aeronautics professor at MIT whose research includes information technology in aviation, said pilots can still talk directly to other pilots in nearby aircraft via radio, and that equipment on the airplane tells pilots if there are airplanes around them.
If a control tower loses radio capabilities, it can also communicate with pilots using high intensity light beams, which send signals to alert whether it’s safe to descend, Hansman said. “We have a number of backup systems that allow the airplanes to fly safely to the extent that air traffic control can still communicate directly with the radio,” Hansman said.
Michael McCormick, a former airspace manager with the FAA, said it could take days for airlines — many of which had to divert flights — to resume normal operations after officials lifted the grounding order.