Regional U.S. air traffic control centers communicate using a complex network that’s “one of the largest telecommunications systems in the country,” and disruptions like those seen on Friday with an hourslong, nationwide grounding of flights can reverberate widely, according to an aviation expert.
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disruptions → communicate → expert
Michael McCormick, a former airspace manager with the Federal Aviation Administration, said it could take days for airlines — many of which had to divert flights — to resume normal operations after officials lifted the grounding order.
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officials → say → order
The order was lifted late Friday.
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order → lift → ?
Here’s a look at what happened, how regional air traffic control centers work, how controllers communicate with pilots and why a problem on the ground can affect flights thousands of miles away among other issues:
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problem → ’ → issues
Top official cites ‘instability’ in communication system
New technology being added to the nation’s air traffic control system overloaded antiquated equipment and caused “intermittent” communications and radar gaps, leading to the ground stop that lasted more than four hours Friday, Trump administration officials said Saturday in a press briefing.
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officials → cite → briefing
Secretary of Transportation Sean Duffy said a contractor had been working on replacing a section of the system’s old copper wire with new fiber wire, and that somehow resulted in the system overload.
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that → say → overload
Duffy said officials were probing whether contractor “incompetence” or a faulty router was the cause.
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incompetence → say → ?
“Specifically, we had over 1,000 connection attempts every 4 to 5 seconds,” Duffy said.
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Duffy → have → attempts
“And what that did was gave us issues with our communication with airplanes, and it also caused some disruption with our radar feeds.
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it → give → feeds
And when we see that, your safety is paramount, we shut down the airspace.”
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we → see → 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.
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Duffy → fly → circumstances
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.
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Congress → work → effort
Miles of old copper wires have been replaced with fiber optic lines, while old radio systems are gradually being replaced at airports.
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systems → replace → airports
But the work is far from complete, and Duffy used the news conference on Friday and Saturday to urge Congress to provide more funding.
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Duffy → use → funding
Regional air control centers play a key role in high-altitude flights
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centers → play → flights
The FAA grounded flights nationwide Friday due to issues at regional air traffic control centers, an FAA notice said.
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notice → ground → centers
The U.S. operates 22 regional air traffic control centers, managed by the FAA, oversees long-distance aircraft operating between departure and arrival airports.
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U.S. → operate → airports
McCormick estimates these control centers take over flights at altitudes over 10,000 feet.
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centers → estimate → feet
These centers, which operate in such places as Anchorage, Alaska, Houston and Indianapolis, are one of the three layers that guide pilots.
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that → operate → pilots
The airport towers direct pilots at the takeoffs at the 500-plus airports that have towers.
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that → direct → towers
Then, the so-called Terminal Radar Approach Control centers take over and guide pilots as they get further away from the airport.
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they → call → airport
And then the regional control centers take over.
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centers → take → ?
When descending, the reverse happens, experts say.
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experts → descend → ?
Experts say that the controllers at the regional centers are sitting at radar displays and are responsible for only that airspace.
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controllers → say → 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.
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Creamer → fly → 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.
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pilot → take → them
Pilots use radio frequency to communicate
McCormick said the country’s regional, high-altitude air traffic control centers need to be connected to remote radio transmitter or receiver sites.
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centers → use → sites
That’s to allow for radio frequency coverage to communicate with the aircraft.
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coverage → ’ → aircraft
Those transmitter sites are connected to the centers via telecommunications systems, the likes of which are in the process of moving from copper wires to fiber optic lines.
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likes → connect → lines
The two-way communication is important to ensure — among other things — that planes maintain safe spacing, he said.
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he → ensure → spacing
“What is especially problematic in this case is that it’s what’s known as a rolling outage,” McCormick said.
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McCormick → ’ → outage
“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.
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it → ’ → center
But he and other aviation experts said that 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.
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controllers → say → radio
A problem on the ground can affect flights thousands of miles away
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problem → affect → miles
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.
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line → lose → workers
That forced the FAA to immediately cancel hundreds of flights going in and out of the airport.
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That → force → airport
But airline experts say that scenario was different from what occurred on Friday.
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what → say → 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 control centers.
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instability → tell → 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,” he said.
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he → say → system
“It propagated around the country.”
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It → propagate → country
…and 10 more, not listed.
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