“Microsoft grappled with a major service outage, leaving businesses, financial firms, airlines and emergency services across the world unable to access computing systems. Thousands of users reported problems with Microsoft 365 apps and services to Downdetector.com, a website that tracks service disruptions.

“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.  The Denver-based airline serves around 120 destinations in the U.S., Caribbean, Mexico and Central America, according to its website. Sun County, another low-cost domestic carrier based out of Minneapolis–Saint Paul International Airport, said in a post on X early Friday that the outage had affected multiple airlines.

“As a result, some of our services are temporarily unavailable. We are working with the third party to resolve this issue as quickly as possible and appreciate your patience,” it said. At Australia’s busiest airport in Sydney, some airline operations and terminal services were being affected Friday afternoon local time, although flights were still arriving and departing, an airport spokesperson said. Qantas, the country’s biggest airline, said it was experiencing “some impacts to systems due to a global software issue that is impacting a number of other businesses.” The airline did not comment on whether flights were operating as scheduled.  The Sydney airport spokesperson said delays were possible later in the day.   “We have activated our contingency plans with our airline partners and deployed additional staff to our terminals to assist passengers,” the person said in an emailed statement. The London Stock Exchange said Friday that a technology issue was affecting the publication of news announcements.