CNN  —  A significant Microsoft outage has brought low-cost carrier Frontier Airlines and some competitors to a standstill, and a regulator halted departures. “Our systems are currently impacted by a Microsoft outage, which is also affecting other companies,” Frontier said in a statement on its website. “We appreciate your patience.” The Federal Aviation Administration said Frontier asked it to pause the airline’s departures across the United States. The airline has cancelled 121 flights Thursday and delayed 225 others, making up 30% of its flights, according to data tracker FlightAware. Allegiant and SunCountry also said on their websites that they were having difficulties. “Due to a global outage at a third party vendor, our booking, check-in, and trip-managing capabilities are temporarily unavailable,” SunCountry said on its site. “The Allegiant website is currently unavailable due to the Microsoft Azure issue,” Allegiant said. Microsoft on its Azure cloud software status report site, said that around 6 pm ET, the service went down for some customers in the Central US region – “including failures with service management operations and connectivity or availability of services.” The company said it determined the cause and is working to fix it. A company spokesman did not immediately respond to a request for comment. Other airlines were unaffected by the outage. United, Southwest and American Airlines said they were not impacted by the outage. This is a developing story and will be updated. CNN’s Zenebou Sylla, Sara Smart, Taylor Romine, Fabiana Chaparro, Jamiel Lynch and Dave Alsup contributed to this report.