Delta Air Lines said it was cancelling nearly 250 flights on Tuesday as it looks to restore operations after a power outage hit its computer systems on Monday, causing the cancellation of about 1,000 flights.
"We were able to bring our systems back on line and resume flights within a few hours yesterday but we are still operating in recovery mode," Delta said in a statement on Tuesday.
An outage hit Delta's computer systems on Monday, grounding planes and stranding passengers of one of the world's largest carriers at airports around the globe.
Delta will be handing out refunds and travel vouchers as penance for the latest computer outage to knock a major airline off stride.
Delta canceled more than 700 flights and had 2,600 others delayed, some for hours, after a power outage Monday at its Atlanta headquarters caused many computer systems to crash.
The computer systems were working again a few hours later but Delta said it was still working to accommodate stranded passengers.
Its challenge Tuesday will be to find enough seats on planes during the busy summer vacation season to accommodate the tens of thousands of passengers whose flights were scrubbed. Last month, the average Delta flight was 87 percent full.
The airline posted a video apology by CEO Ed Bastian. And it offered refunds and $200 in travel vouchers to people whose flights were canceled or delayed at least three hours.
For passengers, hardship from the early morning meltdown was compounded by the fact that Delta's flight-status updates weren't working either. Instead of being able to stay home, many passengers only learned about the flight problems when they arrived at the airport.
"By the time I showed up at the gate the employees were already disgruntled, and it was really difficult to get anybody to speak to me or get any information," said Ashley Roache, whose flight from Lexington, Kentucky, to New York's LaGuardia Airport was delayed. "The company could have done a better job of explaining ... what was happening."
Delta spokesman Trebor Banstetter said that after a power outage at the company's Atlanta headquarters, some key systems and network equipment did not switch over to backup systems. He said the airline's investigation into the cause of the outage was continuing but said there were no indications of hacking.
A spokesman for Georgia Power said that the company believes a failure of Delta equipment caused the airline's power outage. He said no other customers lost power. Delta declined to comment on the power company's report.
Flights that were already in the air when the outage occurred continued to their destinations, but flights on the ground remained there.
At 7 p.m. Eastern time, Delta said it had canceled more than 740 flights, and tracking service FlightStats Inc. counted more than 2,600 delayed flights.
Airlines depend on huge, overlapping and complicated systems to operate flights, schedule crews and run ticketing, boarding, airport kiosks, websites and mobile phone apps. Even brief outages can snarl traffic and cause long delays.
That has afflicted airlines in the U.S. and abroad.
Last month, Southwest Airlines canceled more than 2,000 flights over four days after an outage that it blamed on a faulty network router.
United Airlines suffered a series of massive IT meltdowns after combining its technology systems with those of merger partner Continental Airlines.
Lines for British Airways at some airports have grown longer as the carrier updates its systems.
On Monday in Richmond, Virginia, Delta gate agents were writing out boarding passes by hand. In Tokyo, a dot-matrix printer was resurrected to keep track of passengers on a flight to Shanghai.
Some passengers said they were shocked that computer glitches could cause such turmoil. Others took it in stride.
Ryan Shannon, another passenger on the Lexington-to-New York flight, said passengers boarded, were asked to exit, waited about 90 minutes and then got back on the plane.
Once Delta cleared flights to take off, "we boarded and didn't have any problems. There is always a delay, or weather, or something. I travel weekly, so I'm used to it," Shannon said with a laugh.
Delta said customers whose flights were canceled or delayed more than three hours could get a refund and $200 in travel vouchers. Travelers on some routes can also make a one-time change to the ticket without paying Delta's usual change fee of $200 for domestic flights and up to $500 for international flights.
— Reuters contributed to this report.