Passengers in the Delta Airlines boarding area at McCarran International Airport in Las Vegas are jammed in to wait as Delta Airlines says all its flights are grounded due to a system outage, Monday, Aug. 8, 2016. Delta Air Lines says it is has grounded flights after experiencing unspecified systems issues. (AP Photo/Bree Fowler) Delta Air Lines canceled around 300 flights Monday after its computer systems crashed worldwide, stranding thousands of passengers on a busy travel day.
One of the world's largest airlines said that only 800 of nearly 6,000 scheduled flights were operational.
The flight tracking site FlightStats Inc. said that there were delays on more than 1,000 Delta flights before noon.
About six hours into the outage, limited flights had resumed but widespread delays and cancelations were ongoing.
A power outage at an Atlanta facility at around 2:30 a.m. local time initiated a cascading meltdown, according to the airline, which is also based in Atlanta.
A spokesman for Georgia Power told The Associated Press that the company believes the failure of Delta equipment caused the airline's power outage. He said no other customers lost power.
A Delta spokesman said he had no information on the report.
Many passengers were frustrated that they received no notice of a global disruption, discovering that they were stranded only after making it through security and seeing other passengers sleeping on the floor.
It was unclear if the airline was even able to communicate due to its technical issues, and Delta said that there may be a lag issuing accurate flight status on the company website because of the outage.
Delta planes are parked at gates at Atlanta's Hartsfield International Airport in Atlanta, Monday, Aug. 8, 2016, as Delta Air Lines grounded all flights after after a power outage hit its computer systems globally. (AP Photo/Branden Camp) Flights that were already in the air when the outage occurred continued to their destinations, but flights on the ground remained there.
Airlines depend on huge, overlapping and complicated technology 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 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.
Lines for British Airways at some airports have grown longer as the carrier updates its systems.
In this April 14, 2015, file photo, Delta Air Lines passengers watch as a Delta plane taxis at Atlanta's Hartsfield International Airport in Atlanta. Delta Air Lines grounded flights scheduled to leave Monday, Aug. 8, 2016, after experiencing unspecified systems issues. Confirmation of the troubles came in an official account that responds to customers via Twitter. The airline declined to immediately comment by phone and it was unclear whether all its flights were affected. (AP Photo/Charles Rex Arbogast, File) 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 bad 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," Kopsick said. "Maybe they will let us smoke on the plane, and give us five-star meals in-flight too!"
Passengers line up as they wait to board Delta Air Lines flights at Rome's Leonardo Da Vinci airport, Monday, Aug. 8, 2016. Delta Air Lines has grounded flights and predicted widespread cancellations Monday, disrupting the travel plans of thousands of passengers, after a power outage hit its computer systems globally. (Telenews/ANSA via AP) 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 travelers 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 4 a.m. to catch a flight from Minneapolis and learned about the delays only when she reached the airport and saw media trucks.
Bodeen said that passengers were taking the matter in stride. "It doesn't seem really hostile yet," she said.
The company said travelers will be entitled to a refund if the flight is cancelled or significantly delayed. Travelers on some routes can also make a one-time change to the ticket free of charge.
Investors shrugged off Delta's IT mishap. In midday trading, shares of Delta Air Lines Inc. rose 3 percent to $37.67.
A Delta Air Lines plane takes off at Atlanta's Hartsfield International Airport in Atlanta, Monday, Aug. 8, 2016, as Delta Air Lines grounded all flights after after a power outage hit its computer systems globally. Delta began limited flights amid global computer shutdown; thousands of passengers are stranded with many cancellations and delays are ongoing. (AP Photo/Branden Camp) 
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