All flights from major carriers, including Delta, American, and United, were grounded Friday morning following a massive global technical outage that affected several industries.

The issue reportedly follows an update made by cybersecurity firm CrowdStrike, one of the world’s largest software providers. The disruption caused computer systems using Microsoft Windows to see nothing but the “blue screen of death.” 

Prominent security consultant Troy Hunt said of the disruption, “This will be the largest IT outage in history.” He also noted, “This is basically what we were all worried about with Y2K, except it’s actually happened this time.”

The outage had a global impact, with outages being reported in the UK, India, Germany, and the Netherlands in addition to the United States. 

“We acknowledge how impactful this is for our customers, and we’re working to still receiving obstructions as soon as possible,” Microsoft said in a statement Friday morning, per People.

“The system was sent an update and that update had a software bug in it and caused an issue with the Microsoft operating system. And we identified this very quickly and remediated the issue. As systems come back online and they’re rebooted, they’re working,” founder and CEO of CrowdStrike George Kurtz said during a Today Show interview on Friday morning.

He added, “We’re deeply sorry for the impact that we’ve caused to customers, to travelers, and to anyone affected by this including our company. It is our mission to make sure that every customer is recovered. We’re not going to relent until we get every customer back to where they were.”

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

The outage could impact businesses ranging from airlines to banks, TV stations, healthcare organizations, hotels, and others, and they might lose millions in revenue due to the disruptions. Independent cybersecurity consultant Lukasz Olejnik told Wired this incident should serve as a warning.

“It reminds us about our dependence on IT and software,” Olejnik said. “When a system has several software systems maintained by various vendors, this is equivalent to placing trust on them. They may be a single point of failure—like here, when various firms feel the impact.”