Microsoft cloud outage causes airlines to ground flights

Low-cost carriers Frontier Airlines, a unit of Frontier Group Holdings, Allegiant and SunCountry reported outages that affected operations.

While Frontier said a "major Microsoft technical outage" had hit its operations temporarily, SunCountry said a third-party vendor affected its booking and check-in facilities, without naming the company.

"The Allegiant website is currently unavailable due to the Microsoft Azure issue," Nevada-based Allegiant said in a statement to CNN. Allegiant did not immediately respond to Reuters request for a comment.