An hours-long FAA nationwide ground stop forced airlines to cancel hundreds of flights at Chicago O'Hare International Airport and Midway International Airport before flights resumed on Friday night.
The FAA issued a nationwide ground stop at approximately 3 p.m. Chicago time, due to "extraordinary circumstances and for reasons of safety." The FAA and White House said the issue appeared to be caused by a "telecommunication outage."
The nationwide ground stop came shortly after the FAA issued ground stops at both O'Hare and Midway airports due to a mechanical problem.
The nationwide ground stop was lifted around 7:30 p.m. Chicago time. By then, airlines had canceled 675 flights at O'Hare and 37 flights at Midway, with more than 900 other flights delayed.
The problems that caused the nationwide ground stop were with communication equipment, which means air traffic control centers weren't able to see, track and speak to planes that are in the air. The ground stops at O'Hare and Midway seemed to be early indicators of the problem before it cascaded into a nationwide alert.
Homeland Security Secretary Markwayne Mullin said there was no evidence that a cyberattack was behind the telecommunication outage. He also said there was no connection between the FAA's issues and the lengthy Microsoft outage on Thursday.
Sources tell CBS News an update to the network connecting the ATC system caused a reboot, crash and outage, though further details have not yet been made public.
Audio from air traffic control radio indicated that Chicago was "close to being ATC zero," with no communication equipment working shortly before the ground stop was declared.
Federal officials simply said the system failed because "it's old and outdated" and there is no evidence of a cyberattack.
"When we start looking at cyber threats, cyberattacks, typically some people is going to raise their hand and say, 'Hey, we did that.' There's no chatter. We haven't seen any footprints, as you would say, or identifications of people that got into the system," Homeland Security Secretary Markwayne Mullin said.
Federal authorities said, despite the ground stoppage, the estimated 3,500 flights in air at the time and people at airports were never in danger.
They blamed the outage on an old telecommunications system, which they insist is need of major upgrades.
The FAA said there was an intermittent communication and radar loss, but never a full air traffic control blackout, yet it was serious enough to halt all flights nationwide.
"When you have issues and you can't immediately communicate and immediately see where aircraft are at, that's a risk that we're unwilling to tolerate," Transportation Secretary Sean Duffy said.
Duffy said, while it's safe to fly, the nation must address its aging and outdated air traffic control system or these types of "hiccups" could happen again.
Nationwide ground stops are exceedingly rare, and the most notorious one was issued after the September 11 terrorist attacks in 2001. But officials said Friday's ground stop was not akin to what happened on 9/11, as airplanes were not being told to land immediately at the first available airport.
Instead, this ground stop was due to problems affecting the in-route communication system: the high-altitude tracking that is done at 20 air traffic control centers across the country as well as in Alaska and Hawaii.
Passengers in the air were not in any danger during the ground stop, officials said, and there was no national security threat.
Homeland Security Secretary Markwayne Mullin emphasized as he spoke to reporters Friday evening that this was a telecommunications outage affecting the ability for air traffic controllers and planes to communicate. Transportation Secretary Sean Duffy said the ground stop was issued "out of an abundance of caution."
Mullin also said they do not have indications that what happened was the result of a cyberattack.
Even though main radio communications went down, planes were not without the ability to communicate at all. Planes, air traffic controllers, and airports use the ACARS system, which stands for Aircraft Communications Addressing and Reporting System, and has been in place since the 1970s. ACARS is essentially a VHF-based text messaging system for aircraft that allows them to send messages back and forth without using voice communication frequencies.
It's not just pilots who can use ACARS; flight crews can also use it to communicate with their airline master command centers and help get information to passengers in the air and on the ground.
At O'Hare and Midway, planes already set to take off when the ground stop was issued were being routed to park in overflow lots until they were given clearance to depart. Many flights that were preparing for takeoff when the ground stop was issued were deplaned so that passengers could wait inside the airport.
But the ground stop will likely have a domino effect on air travel through the weekend. DePaul University professor and transportation expert Joe Schwieterman – who spoke with us from Midway Airport where he himself was stranded as a passenger – said Friday and Sunday are the busiest travel days of the weekend and the flight delays and cancellations will quickly pile up.
"Airlines can respond to outages that last about 90 minutes to two hours," he said. More than that and pilots and flight crews can't legally fly, airline maintenance guidelines can't be met, and the situation starts to cascade.
He said if the ground stop was lifted by 6 p.m. Chicago time, it would be possible for airlines to recover and be able to operate a fairly normal Saturday schedule, but it seems unlikely.
Schwieterman said passengers largely seemed to be staying outside the security area at Midway, avoiding getting stuck past TSA checkpoints and having their baggage in the checked bag system. He also noted that the situation he and so many others were in on Friday is "really a rare thing."
"I have to say that not having a backup system for something like this is really pretty galling," he said. "That was the whole goal of the federal government 10 years ago. Regional outages, airline-specific outages [are one thing] but a national outage shouldn't occur from a single glitch."
At O'Hare passengers were also lingering before check-in. Many heard the news on their way to or as they arrived at the airport. They're holding back to avoid checking their bags and get locked into air travel that likely won't happen.
One group of women headed to Louisville, Kentucky, for a 21st birthday party told CBS News Chicago they were changing plans and renting a car instead, planning to drive all night to make the event. One of their group had checked their bag already, but they planned to just deal with that as they go.
"It's kind of madness, kind of what I expected I guess. It's just kind of unfortunate. It's just like, I don't know, you can't just bail when you don't know what you're going to get," said Deacon Lobdell, who is trying to fly to Tennessee. "I'm flying United. I got a text from them saying they'll send us an update probably around 7 p.m., so I don't really know what to do. Probably just wait around."
"It's kind of stressful, just cuz it's never- I guess it's happened before, many years ago, but I don't know," said Zubair Kahn, who was flying to Paris also on United. "It's a strange thing to walk into."
"Yeah we're thinking probably go home, rebook, and probably see how it plays out tomorrow," said Frank Foto, who had planned to fly to Miami (with his baby) for a cruise.
But some people were still lined up at TSA to go through security, deciding to wait it out on the other side at their gates. But with no clear timeline, it's not very clear both to airlines and travelers what the wisest decision could be.
It was a mad dash for travelers to grab hotel rooms and rental cars after the ground stop went in place and they were left in limbo with no answers.
Even after flights resumed, many travelers were still frustrated.
"We checked in, but we didn't want to go through security, because we didn't want to lose our bags. So, we're just waiting around here. But there's been no real updates. United's not really giving us any updates either," said Zubair Kahn, who was traveling to Paris.
The impact of what happened on Friday will continue for days.
Frank Foto and his baby, Theo, were heading to Miami to catch a cruise on Saturday, but were left unsure if they can make it.
"We're thinking probably go home, rebook, and maybe see how it all plays out tomorrow," Foto said.
At O'Hare's baggage claim, crowds waited for their belongings on top of other ordeals during an excruciatingly long day.
"We were going to Nashville for a birthday party, we got stuck on the tarmac for about 4 ½ hours, and now I can't even find my bag," Gerald Hill said.
What was it like on the plane?
"Hot, cramped, tired. I was ready to get out, but we couldn't get off the plane, because they had no gate for us to go to. So, we were stuck there for hours," Hill said.
Airport staff tried answering questions for confused travelers, including Lucas and Laura, who were part of a long line of people trying to locate checked bags as they waited to get home to Brazil.
"We've been rescheduled for Tuesday, because we opted for it, but we wanted our bags to stay with us until Tuesday, and we can't," Lucas said.
The two will be without their bags for days but are grateful to have a place to stay in the meantime.
"We are very exhausted after a long trip. We just wanted to go home. But it's okay. At least we have a friend who lives near here, and we're going to her house," Laura said.
The backlog for luggage at O'Hare was so great that some staff were telling people that they could leave and return on Saturday to retrieve their belongings.
