Microsoft grappled with a major service outage, leaving users across the world unable to access its cloud computing platforms and causing airlines to cancel flights.

Thousands of users across the world reported problems with Microsoft 365 apps and services to Downdetector.com, a website that tracks service disruptions.

Microsoft shares dropped 2% in premarket trading Friday.

"We ’ re investigating an issue impacting users ’ ability to access various Microsoft 365 apps and services," Microsoft 365 Status said on X early Friday.

On its status page for Azure, Microsoft ’ s cloud computing platform, the company said the issue began just before 10 p.m. ET Thursday, affecting systems across the central U.S. In an update, Microsoft said it had determined the cause and was working to restore access to its users.

Microsoft didn ’ t respond immediately to a request for comment.

The outage forced low-cost airline Frontier to cancel some flights. "Our systems are currently impacted by a Microsoft outage, which is also affecting other companies," Frontier said in a statement. "We appreciate your patience." The carrier said it would offer refunds to affected passengers.

The Federal Aviation Administration said Frontier asked it to pause the airline ’ s departures across the U.S. Thursday night. The ground stop was later lifted.