Flights to resume at Chicago O'Hare, Midway airports after FAA lifts nationwide ground stop

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.  

FAA issues nationwide ground stop, a rare order

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 group stop is not akin to what happened on 9/11, as airplanes are not being told to land immediately at the first available airport.

Instead, this ground stop is 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.  

According to the FAA, all departing flights are stopped until further notice. Inbound flights will be managed on a case-by-case basis. 

Passengers in the air are not in any danger, officials said, and there is no national security threat.

Homeland Security Secretary Markwayne Mullin emphasized as he spoke to reporters Friday evening that this is a telecommunication outage affecting the ability for ATC and planes to communicate. Duffy said the ground stop was issued "out of an abundance of caution."

Mullin also said there they do not currently have indications that this is because of a cyberattack.

Even though main radio communications are down, planes are not without the ability to communicate at all. Planes, air traffic controllers and airports use the ACAR system, which stands for Aircraft Communication Addressing and Reporting and has been in place since the 1970s. ACAR is essentially a VHF-based text messaging system for aircrafts, which allows them to send messages back and forth without using the oral communication frequencies.

It's not just pilots that can use ACAR; 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. 

Major air travel disruptions expected to last through the weekend

At O'Hare and Midway, planes set to take off are being routed to park in overflow lots until they are given clearance to depart. Many flights that were preparing for takeoff have also been deplaned so that passengers can wait at 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 cancelations 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 is lifted by 6 p.m. CT it's possible the airlines could recover and be able to operate a fairly normal Saturday schedule, but it seems unlikely.

Schwieterman said passengers largely seem to be staying outside the security area at Midway, avoiding get stuck past TSA and having their baggage in the checked bag system. He also noted that the situation he and so many other are in 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.