Thousands of Delta passengers stranded as power outage crashes computer network
Delta Air Lines cancelled around 365 flights after its computer systems crashed worldwide, stranding thousands of passengers.
Limited flights have resumed but the airline said widespread delays are ongoing and there may be more cancellations.
A power outage at an Atlanta facility at around 2.30am local time initiated a cascading meltdown, according to the airline, which is also based in the city.
A spokesman for Georgia Power said the company believes a failure of Delta's own equipment caused the power outage as no other customers were affected.
Many passengers were left frustrated after receiving no notice of the global disruption, only discovering that they were stranded after making it through security and seeing other passengers sleeping on the floor.
It is unclear if the airline was even able to communicate due to its technical issues, and Delta said there may be a lag issuing accurate flight status on the company website because of the outage.
Flights that were already in the air when the outage occurred continued to their destinations, but those still on the ground remained there.
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 US and abroad.
Last month, Southwest Airlines cancelled more than 2,000 flights over several days after an outage that it blamed on a faulty network router.
United has suffered a series of notorious delays since it merged with Continental as the technological systems of the two airlines clashed.
Queues 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.
Technology that appeared to be working sometimes issued incorrect information. Flight-status systems, including airport screens, incorrectly showed flights on time.
"Not only are their flights delayed, but in the case of Delta the website and other places are all saying that the flights are on time because the airline has been so crippled from a technical standpoint," said Daniel Baker, CEO of tracking service FlightAware.com.
Delta issued an apology to customers and said teams were attempting to fix the problem as quickly as possible.
Many passengers, like Bryan Kopsick, 20, from Richmond, were shocked that computer glitches could cause such turmoil.
"It does feel like the old days," Mr Kopsick said. "Maybe they will let us smoke on the plane, and give us five-star meals in-flight too."
In Las Vegas, stranded passengers were sleeping on the floor, covered in red blankets. When boarding finally began for a Minneapolis flight - the first to take off - a Delta worker urged people to find other travellers who had wandered away from the gate area, or who might be sleeping off the delays.
Word of the extensive breakdown began to spread after the airline used a Twitter account to notify customers that its IT systems were down "everywhere". Technological issues extended even to the company's website.
Tanzie Bodeen, 22, a software company intern from Beaverton, Oregon, left home at 4am to catch a flight from Minneapolis and learned about the delays only when she reached the airport and saw media trucks.
Ms Bodeen said that passengers were taking the matter in their stride. "It doesn't seem really hostile yet," she said.
The company said travellers will be entitled to a refund if the flight is cancelled or significantly delayed, while those on some routes can also make a one-time change to the ticket free of charge.