A system-wide computer outage has delayed Delta flights around the world, leaving thousands of passengers stuck in airports as they wait to board their planes. The US airline says the glitch was caused by a power outage in Atlanta at 2:30AM ET this morning, and "impacted Delta computer systems and operations worldwide." The company says it's working on a fix, but expects "large-scale cancellations" today, advising passengers to check the status of their flight before heading to the airport. Flights already on their way to their destination are unaffected.

Due to a computer outage, flights awaiting departure are currently delayed. Flights enroute are operating normally. — Delta News Hub (@DeltaNewsHub) August 8, 2016

Due to a computer outage, flights awaiting departure are currently delayed. Flights enroute are operating normally. — Delta News Hub (@DeltaNewsHub) August 8, 2016

In a blog post, Delta said: "We are aware that flight status systems, including airport screens, are incorrectly showing flights on time. We apologize to customers who are affected by this issue, and our teams are working to resolve the problem as quickly as possible."

Delta passengers on Twitter have been complaining of long queues in airports around the world, with airline staff reportedly unable to check in passengers. One Delta customer, 40-year-old Luciano Resende, told NBC News that Delta employees in Heathrow had begun to complete this process by hand, but that progress was slow. "I guess it has been a long time since they used the manual process," said Resende. A computer glitch that hit Southwest airline last month led to more than 900 flight cancelations.

Update August 8th, 7:13AM ET: Updated to include new info from Delta.