A global technology outage impacting airports, banks and hospitals around the world continued Friday morning, leading to hundreds of delayed and canceled flights at Denver International Airport.

Cybersecurity firm CrowdStrike said the issue believed to be behind the outage was not a security incident or cyberattack — and that a fix was on the way. The company said the problem occurred when it deployed a faulty update to computers running Microsoft Windows.

“Operations have largely stabilized at DEN amid worldwide technology issues,” the airport said in a 7:49 a.m. update. “Airline ground stops have lifted at DEN — but delays are still impacting travelers.”

DIA first noticed an issue Thursday night when Frontier Airlines announced its systems were being impacted by a Microsoft outage, including booking, check-in, access to boarding passes and some flights.

Frontier asked the Federal Aviation Administration to issue a ground stop for the airline Thursday night, which was lifted around 10:18 p.m., according to the carrier.

Friday morning, issues at the Denver airport continued with 522 flights delayed and 99 flights canceled by noon.

According to the FAA, as of noon, flights headed to Atlanta were experiencing average delays of more than six hours, and flights headed to New York and Minneapolis were seeing average delays of more than two hours.

United led the charge Friday morning with 251 flight delays, and 113 Southwest flights failed to leave the gate on time, according to data from flight tracking software FlightAware. Regional airline SkyWest, the airline that operates United Express, also delayed 70 flights.

United had the most flights canceled Friday morning, with 56 flights, followed by Delta’s 26 canceled flights.

American Airlines — which delayed 13 flights and canceled five Friday morning — also confirmed it was affected by the outage. The airline said it resumed normal operations around 3 a.m. Friday.

Southwest, United, Delta, Frontier, SkyWest, Icelandair, Key Lime Air, Alaska Airlines, Air Canada, Swiss, WestJet, Allegiant Air, Volaris and Air France all canceled or delayed flights Friday morning as well.

“A third-party outage is impacting computer systems, including at United and many other organizations worldwide,” United Airlines said in a statement on social media at 4:26 a.m. Friday. “As we work to fully restore these systems, some flights are resuming. Many customers traveling today may experience delays.”

Hundreds of passengers were stranded in the airport overnight Friday, sleeping on the floor or on chairs and benches, according to United passenger Cayle Hunter.

Hunter was flying Thursday from Sacramento to North Carolina and said he had a layover in Denver scheduled to take off around midnight.

“We boarded the plane and sat there for two hours,” Hunter said. “They deboarded us and all of our flights were immediately canceled. … I slept for an hour or two on the airport floor and have been frantically refreshing the app since 5 a.m. trying to book a flight that will get me to Raleigh earlier or get me back home.”

Hunter said the airline was offering no compensation to any passengers since the delays were out of United’s control. He said he was frustrated with the lack of communication.

“I’m pretty easygoing, but it was past 2 a.m. so I knew I was stranded, which was completely demoralizing,” Hunter said. “I’m traveling for a one-time event that starts at 7 p.m. tonight. I just found and booked a direct flight that gets me there at 3. It’s already been delayed.”

Microsoft 365 posted on social media platform X that the company was “working on rerouting the impacted traffic to alternate systems to alleviate impact” and that it was “observing a positive trend in service availability.”

CrowdStrike CEO George Kurtz said in a statement on X that the company “is actively working with customers impacted by a defect found in a single content update for Windows hosts.”

He said: “This is not a security incident or cyberattack. The issue has been identified, isolated and a fix has been deployed.”

More than 800 flights were canceled or delayed at DIA on Thursday.

The Associated Press contributed to this report. 

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