Delta passengers stranded due to power outage

Delta Airlines cancelled hundreds of flights and delayed many others on Monday after a power outage caused its computer systems to crash.

The power failure started around 0630 GMT in Atlanta, Georgia, near the company's headquarters.

Thousands of people were left stranded at airports around the world as flights across the US, Japan, Italy and the UK were delayed or cancelled.

Passengers flooded social media with complaints about long check-in queues.

The initial flight grounding order was lifted about six hours after the system failure. Although some fights resumed, cancellations and delays still continue.

The company said it is cancelling nearly 250 more flights on Tuesday as it looks to restore operations.

"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 stated.

Delta is the second-largest US airline by passenger traffic. It has more than 15,000 flights a day along with its alliance partners.

The company promised to provide 200 dollars vouchers to the customers whose flights were cancelled or delayed for more than three hours. Passengers who booked to travel between August 8-12 will also be entitled to get a refund.

Travelers on some routes will be able to make a one-time change to their tickets without paying the usual change fee.

In a video message posted online, Delta CEO Ed Bastian apologised for the inconvenience. "I apologise for the challenges this has created for you with your travel experience," he said.

According to Georgia Power, an electric utility that provides power to most counties in Georgia, the problems arose after a switch gear, which helps control and switch power flows like a circuit breaker in a home, malfunctioned for reasons that were not immediately clear.

The problem has caused a shutdown Delta's data centre, which includes the company's website, smartphone apps, airport check-in systems and passenger advisory screens. No other Georgia Power customer has been affected.

Both Delta and Georgia Power announced that an investigation into the cause the system-wide outage is underway.

Computer outages disrupting flights are not uncommon. Last May, air traffic throughout Sweden was halted due to a glitch affecting the country's civil aviation authority radar site.

In March, a computer system failure forced Japan-based All Nippon Airways to cancel more than 100 domestic flights, stranding about 16,000 passengers.

Last year, hundreds of flights at US east coast airports were delayed for several hours due to a computer system problem at a regional air traffic control centre.