Normal air traffic is "resuming gradually" after an overnight outage to the Federal Aviation Administration's Notice Air Missions (NOTAM) system -- an essential system that alerts pilots to crucial information like potential hazards on flight routes -- led to a "pause in domestic departures" at airports across the country.
In a series of statements, the Chicago Department of Aviation and the FFA both around 8 a.m. Wednesday confirmed that a "ground stop" had been lifted.
However, the CDA said, "residual delays or cancellations will likely continue throughout the day as a result of this morning's outage."
That means if you're flying in or out of O'Hare or Midway International Airports Wednesday, you're going to want to check your flight status.
Here's what we've learned happened, and where things currently stand.
What the FAA Says Happened
According to a statement from the FAA, its NOTAM had "failed" Wednesday morning. As a result, all flights in the U.S. had been grounded following the incident, a source with knowledge of the situation told NBC News. By 6:19 a.m. the FAA announced that all airlines had been ordered to "pause domestic departures until 9 a.m. Eastern Time"
Local
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In the 7 a.m. hour, the FAA said it was "making progress" in restoring its system following an "overnight outage," with departures resuming at some airports.
Just before 8 a.m. CST, the FAA indicated that "normal air traffic operations" had begun to "resume gradually."
According to a report from the Associated Press all domestic aircraft are required to route through the NOTAM system, including commercial and military flights.
Flight Delays at O'Hare, Midway
Although the FAA's ground stop has been lifted, delays in the hundreds continue to pile up at Chicago airports.
As of 9 a.m., FlyChicago shows O'Hare International Airport with 661 total flight delays, and Midway with 284 total delays.
At O'Hare, flight status screens are showing the phrase "Technology issue" across multiple flights.
"Check your flight status if you're traveling today, "Mitchell Airport in Milwaukee tweeted shortly after the FAA issued their initial statement. "FAA is preventing aircraft from departing at airports nationwide."
United Airlines tweeted a similar message Wednesday, saying "The FAA system that sends out important real-time flight hazards & restrictions to all commercial airline pilots -- Notice to Air Missions (NOTAM) -- is currently suffering a nationwide outage. United has temporarily delayed all domestic flights."
Secretary of Transportation Pete Buttigieg said in a tweet that he was in touch with the FAA, and that it was "working to resolve this issue swiftly and safely so that air traffic can resume normal operations."
A tweet from the White House Wednesday morning indicated that President Biden had been briefed on the outage, saying that "there is no evidence of a cyberattack at this point." The tweet went on to say that the President Biden "directed DOT to conduct a full investigation into the causes."
International Flights
The Associated Press reports that European flights into the U.S. appeared to be largely unaffected.
Irish carrier Aer Lingus said services to the U.S. continue, and Dublin Airport’s website showed that its flights to Newark, Boston, Chicago and Los Angeles were running on schedule.
“Aer Lingus plan to operate all transatlantic flights as scheduled today,” the carrier said in a prepared statement. “We will continue to monitor but we do not anticipate any disruption to our services arising from the technical issue in the United States.”
Flights Currently in the Air
According to the FAA, "all flights currently in the sky are safe to land," as the NOTAM system is used by pilots prior to a flight taking off.
This is a developing story that will be updated as more information becomes available.
