The airline said early Monday that all departing flights have been delayed by a global computer system outage.

"Our systems are down everywhere," it tweeted in response to disgruntled customers.

Passengers on Twitter reported problems -- including the inability to check in or being stuck on the tarmac -- from airports around the world, including San Francisco and Athens.

"Flights awaiting departure are currently delayed," the airline said in a statement. "Flights en route are operating normally."

Delta (DAL) advised customers to check the status of their flights while it tried to fix the problem.

Reports of delays on social media appeared to have begun around 3 a.m. ET.

Delta's problems come less than three weeks after Southwest Airlines canceled more than 1,000 flights following a system outage.