Thousands of Delta Air Lines customers, stranded for hours Monday, can blame larger and more sophisticated airline computer systems, along with increased consolidation of air carriers.
The Atlanta-based carrier reported a computer outage early Monday that caused more than 650 flights to be canceled and more than 2,000 to be delayed. By the end of the day, the system was back online but the ripple of delays continued.
"I apologize for the challenges this has created for you with your travel experience," Delta Chief Executive Ed Bastian said in a video statement posted on the airline's website. "The Delta team is working very, very hard to restore and get these systems back as quickly as possible."
Several computer applications were affected, including the company's website.
Delta initially said the problem was caused by a power outage in Atlanta. A spokesman for Georgia Power, however, said the outage was limited to Delta's Atlanta systems and was caused by the failure of the airline's equipment.
Computer-related cancellations and delays have become more common in the past few years as airlines increasingly rely on larger, more complicated computer systems that are tied into airport kiosks and smartphone apps, according to airline experts.
Because of industry consolidation in the last decade, a shutdown at any of the major carriers now has a bigger effect on travelers, particularly at hub airports dominated by one airline. The nation's four biggest carriers — American Airlines, Delta, Southwest Airlines and United Airlines — carry nearly 80% of the country's domestic air travelers.
Hardest hit was Delta's home-base airport, Hartsfield-Jackson Atlanta International Airport, where 73% of passengers annually fly Delta. But more than two dozen flights were also canceled at Los Angeles International Airport, and airports around the world were affected, with airline employees turning to pen and paper for tasks normally handled by computer.
"Today you have four airlines controlling about 80% of the domestic market," said Bijan Vasigh, a professor of air transport economics at Embry-Riddle Aeronautical University. "Passengers don't have that many choices."
Airline industry analyst Bob Mann said airlines are supposed to have systems in place to limit the damage from such outages.
"It shouldn't have taken down the entire network," said Mann, a former airline executive and principal of R.W. Mann & Co. "It should cause the organization to review how this sort of single-point failure could occur and what didn't work as anticipated."
Delta is known in the industry for its punctuality, which should help it withstand the blow to its reputation, said David Primo, an associate professor of political science and business administration at the Simon Business School at the University of Rochester.
"They've got a bit more insulation than other airlines," he said.
Instead, the pain will fall mostly on travelers such as Stephen Smith, 32, of Baton Rouge, La.
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 said he 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 point," he tweeted to the Associated Press.
The outage stranded Alexsey Gromov, a 27-year-old aerospace engineer from Long Beach, at Lihue Airport in Kauai. He slept on a bench outside because he said the airport floor was too filthy.
"It's completely unreasonable for them to keep us six hours in the airplane and tell us our flight is canceled and by then all the rooms are booked and your only option is to stay in the airport until further instructions," he said.
Customers whose flights were canceled or "significantly delayed" will receive refunds or vouchers for future travel, Delta said. The airline is also allowing customers to reschedule flights by Friday without paying the typical change fee.
Computer outages have caused major headaches for airlines and travelers before. Southwest Airlines had 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.
Last summer, United Airlines blamed a failed computer internet router for the cancellation of several dozen flights.
Delta reported a computer problem in 2014 that produced super-cheap fares, while Alaska Airlines had a computer glitch that offered a promotional deal that expired before passengers could book it.
Experts have blamed the rash of outages on massive, interconnected computer systems that lack sufficient staff and financial backing.
Times staff writer Helen Zhao and the Associated Press contributed to this report.
4:50 p.m.: The story was updated to include the latest cancellation and delay numbers as well as new analysis.
1:35 p.m.: This story was updated with comments from Delta, industry analysts and a customer.
9:50 a.m.: This article was updated with comments from Georgia Power and airline industry analyst Bob Mann.
7:50 a.m.: This article has been updated with Times staff reporting.
6:15 a.m.: This article has been updated with Delta beginning limited flights.
4:10 a.m.: This article has been updated throughout with additional details and background.
3:25 a.m.: This article has been updated with more information about the delays and comment from a passenger.