“We want our customers to know we are thoroughly investigating the matter and that we are truly sorry,” said Delta chief operating officer Gil West in a written statement.
While it resumed flights and said its systems are fully operational, Delta also said Monday afternoon that delays and cancellations remain as it recovers. The airline said it was focusing on improving operations at its Atlanta hub to reduce further delays.
“While systems are improving and flights are resuming, delays and cancellations continue,” the airline had said at Noon.
Delta advised customers to check their flight status before heading to the airport.
Monday mornings are a peak period for business travelers starting the work week, as well as for vacationers returning from weekend trips and others.
The computer system failure was due to a power outage in Atlanta that began at about 2:30 a.m., according to Delta.
“Following the power loss, some critical systems and network equipment didn’t switch over to Delta’s backup systems. Delta’s investigation into the causes is ongoing,” the company said in a written statement.
The airline said those travelers whose flights are cancelled or “significantly delayed” are entitled to a refund.
For any travelers with flights booked on Delta on Monday, Delta is waiving certain change fees for those who want to reschedule their flights to leave later this week.
Delta released a video message at 1:30 p.m. from its CEO Ed Bastian apologizing for the inconvenience to customers.
“The Delta team is working very, very hard to restore and get these systems back as quickly as possible,” Bastian said in the video. He called it in “all hands-on deck effort.”
The question of when Delta can resume its regular flight schedule in full and when delays will end will depend on not just the relaunch of the computer systems, but also the availability of crews whose work hours are subject to federal limits, and other factors.
Conor Bergin, of Atlanta, said he was already at the airport planning to head to Minneapolis, Minn. when he saw winding lines and soon got a news alert about all flights being grounded.
“You always expect a bit of a line at the airport but not like this,” he said.
“Hopefully this doesn’t become a theme or a reoccurring issue,” Bergin said.
Bastian said the power outage caused the airline to put in place a ground stop at 5 a.m., halting any flights from taking off. Flights en route were continuing to their destinations. Delta announced at 8:40 a.m. that the ground stop had been lifted and that limited flights were resuming.
Georgia Power spokesman John Kraft said a failure overnight of switch gear equipment caused the outage. He said other Georgia Power customers were not affected because it was an issue with Delta equipment, and said Georgia Power crews were on site working with Delta to repair the equipment.
The Delta computer outage comes after Southwest Airlines suffered a massive computer outage last month that grounded its fleet nationwide and had widespread repercussions on its flights for days.
Delta is the largest airline at Hartsfield-Jackson International Airport and Dallas-based Southwest is the second-largest.
At Hartsfield-Jackson mid-morning, a long line of customers seeking customer service stretched through the Delta check-in area. Other Delta passengers were using check-in kiosks, getting boarding passes and proceeding to their gates on the concourses, even though many flights were still delayed.
With some travelers stranded at airport gates awaiting flights, Delta said it was deploying carts to offer refreshments and beverages to customers.
Some customers were frustrated with the lack of communication from Delta about the status of their flights Monday morning.
Delta said in the afternoon that customers “can now check the status of their flight and conduct some rebooking options” on its website or its app. For those whose flights have been changed or rebooked, Delta said customers’ original boarding passes will work at the gate for their new flights.
Delta also said unaccompanied minors scheduled to fly today would not be able to fly, and can rebook their flights for a later date.
The AJC’s John Spink contributed to this article.