All departing Delta Airlines flights were grounded Monday morning after a computer system outage struck its Atlanta hub. The world's second largest airline said there would be "large-scale cancellations" as passengers scrambled to look up flight information. 

"Our systems are down everywhere," Delta's Twitter account posted in response to confused customers. "Large-scale cancellations are expected today."

The computer failure affected several applications, including the company's website, the Associated Press reported. Passengers in airports around the world, including San Francisco, Rome and Athens, reported being stuck on tarmacs, getting incorrect information from Delta officials and sleeping on airport floors.  In one case, the airline delivered pizza to waiting passengers, CNN reported.  

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

Flight status information could be found here. Delta said it would issue a waiver to affected customers. Updates from the company can be found here. 

The Joseph family from Suffern, New York, told CNN they were waiting at LaGuardia Airport in New York for a flight to Orlando for their Disney World vacation with their six children.

"Delta is just saying the systems are down and we are going to be late," said Frantzy Joseph, the family's father.

In New Jersey, Cynthia Towles was waiting at the Newark Airport for a flight to St. Thomas in the U.S. Virgin Islands. "They didn't tell us anything. I didn't get an email, I didn't get anything. Nothing," she told local reporters.

In London, Luciano Resende, 40, told NBC News the airline had started to manually check-in customers for their flights. He was traveling home to San Francisco via Seattle.

"I guess it has been a long time since they used the manual process," Resende said of the delays.