Airlines begin to resume service after a massive global IT outage disrupts computer systems

A massive IT outage is causing disruptions across the world, impacting flights, banks and other major institutions.

Amid the outage, the Federal Aviation Administration said that several airlines requested assistance with ground stops for their fleets until the issue is resolved. Many major airlines said they will offer travel vouchers this weekend, allowing passengers to adjust their itineraries without paying change fees.

FlightAware reported that nearly 1,300 U.S. flights have been canceled as of early Friday morning. Additionally, more than 2,900 flights have been delayed.

Even as service begins to resume this morning, United Airlines cautioned passengers that disruptions to service could last throughout the day. Delta said shortly before 8 a.m. ET that it is beginning to resume departures, but that additional delays are expected throughout Friday.

Also, numerous police departments across the U.S. have reported that the outage has affected their 911 service. Many police departments are encouraging the public to contact them via non-emergency lines until the outage is resolved.

Microsoft 365 said early Friday that services were starting to return to normal.

"The underlying cause has been fixed, however, residual impact is continuing to affect some Microsoft 365 apps and services. We're conducting additional mitigations to provide relief," the company said.

The outage was linked to cybersecurity firm CrowdStrike. The company's CEO said the outage was not due to a security incident.

"CrowdStrike is actively working with customers impacted by a defect found in a single content update for Windows hosts. Mac and Linux hosts are not impacted. This is not a security incident or cyberattack," CrowdStrike CEO George Kurtz said. "The issue has been identified, isolated and a fix has been deployed ... Our team is fully mobilized to ensure the security and stability of CrowdStrike customers."

The U.S. Department of Homeland Security released a statement Friday morning.

"The Department, and the Cybersecurity and Infrastructure Security Agency are working with CrowdStrike, Microsoft and our federal, state, local and critical infrastructure partners to fully assess and address system outages," the department said.