Flights from several major U.S. airlines, including Delta, United, and American Airlines, were grounded Friday due to a communication issue, the Federal Aviation Administration (FAA) said.
The issue is affecting all flights from the airlines, regardless of their destinations, CNN reported. Flights in the air will stay in the air, but no American, United, or Delta flights will take off, the FAA said.
The duration of the ground stop is currently uncertain, but the FAA said an update would be provided by 5 a.m. ET.
This follows a major Microsoft outage Thursday that halted Frontier Airlines operations for several hours. Frontier's systems were disrupted by the outage, leading to offers of refunds for affected passengers.
The ground stop was lifted late Thursday night.
"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 company was offering refunds to inconvenienced passengers.
The airline canceled 131 flights and delayed 223 others Thursday, affecting nearly 30% of its operations, according to CNN.
Competitors Allegiant and SunCountry also faced challenges, including issues with their online booking, check-in, and trip management functions.
"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 website.
The FAA announced Friday morning that all Allegiant flights would be grounded as well. "The Allegiant website is currently unavailable due to the Microsoft Azure issue," the airline said.
According to Microsoft's Azure cloud software status report, services for some customers in the central United States went down around 6 p.m. ET on Thursday. This included failures in service management operations and connectivity. Microsoft said that it had identified the cause and was working on a fix.
Passengers are advised to check with their respective airlines for updates on flight statuses and possible delays.
