An issue with Microsoft’s Azure system also affected the check-in and booking systems at Allegiant and Sun Country Airlines. On Thursday, Frontier Airlines temporarily halted all flights due to a significant outage in Microsoft networks, which also disrupted computer systems at low-cost carriers Allegiant Air and Sun Country Airlines.

According to Microsoft’s Azure status page, this issue started at around 6:00 p.m and impacted various systems for customers located in the central United states.

“Our systems are currently impacted by a Microsoft outage, which is also affecting other companies. During this time booking, check-in, access to your boarding pass, and some flights may be impacted,” Frontier Airlines said in a post on X.

According to a notice on the Federal Aviation Administration’s website, the airline implemented a temporary ground stop for all its flights, which was lifted approximately 35 minutes later.

Airlines occasionally issue these instructions to temporarily suspend flights due to technical issues. Frontier did not disclose the number of flights and passengers affected thus far. The Denver-based airline operates a fleet of over 100 planes, according to its website.

The Microsoft outage impacted at least two additional airlines.  “One of our information vendors is experiencing a global outage affecting multiple airlines. As a result, some of our services are temporarily unavailable,” Sun Country said.

Allegiant stated on X that customers might experience issues with check-ins, bookings, and obtaining boarding passes.