LONDON (AP) — Delta Air Lines has grounded flights and predicted widespread cancellations today after a power outage hit its computer systems globally, disrupting the travel plans of thousands of passengers.

The Atlanta-based carrier said in a statement that the outage began at around 2:30 a.m. Eastern. Flights which were already en route were operating normally, but many passengers took to Twitter to express frustration with being stuck on the ground.

“We are aware that flight status systems, including airport screens, are incorrectly showing flights on time,” the company said in a statement. “We apologize to customers who are affected by this issue, and our teams are working to resolve the problem as quickly as possible.”

Confirmation of the trubles first came in an official account that responds to customers via Twitter. The company had said its IT systems were down “everywhere” and “hopefully it won’t be much longer.”

Several applications were affected, including the company’s website.

Among those affected by the situation was Stephen Smith, 32, of Baton Rouge, Louisiana. He had been stuck on the ground for about three hours at Tokyo’s Narita Airport on a flight that was supposed to go to Shanghai.

Smith took solace in the fact the air conditioning on the plane was working and said it seemed everyone on board was fine.

“Waiting game at this pint,” he tweeted to The Associated Press.

Airline data company Flightaware said there were at least 858 cancellations and 7,359 delays across the global industry on Monday morning. It’s unclear how many are related to Delta’s problems and whether Delta’s groundings are reflected in the numbers.

Computer outages have caused major headaches for airlines and travelers before. Southwest Airlines was forced to cancel more than 2,000 flights across the U.S. last month after technology problems prevented many travelers from checking in or boarding flights.