[NEW YORK] Delta Air Lines Inc's flights gradually began taking off again on Monday after a power outage hit its computer systems, grounding planes and stranding passengers of one of the world's largest carriers at airports around the globe.
The US airline said the power outage began at about 2:30 am EDT (0630 GMT) in Atlanta and that customers should expect "large-scale" cancellations.
Delta said in an update at 8:40 am EDT (1240 GMT) that a halt on departures had been lifted, and some flights were resuming, although customers should expect delays and cancellations.
The company said via Twitter that it had cancelled about 300 flights due to the power outage.
The problems also meant flight information was not showing correctly on Delta's website or on airport information boards, and this could also take time to resolve, the carrier said in the latest update.
According to website Flightradar24, some of the first flights to take off were from Amsterdam to the United States, while a flight from Phoenix to Atlanta was among the first to depart from a US airport.
Delta operates 5,000 departures a day and is a member of the SkyTeam alliance alongside airlines including Air France-KLM .
It also partners for transatlantic flights with Virgin Atlantic, which said its flights were operating normally but cautioned that passengers should check tickets in case their flight was due to be operated by Delta as part of a code-share agreement.
Delta said passengers booked for travel Aug 8-12 would be entitled to a refund if their flight is cancelled or significantly delayed.
Its shares were up 0.2 per cent at US$37.73 in morning trading.
In airports around the world, passengers stuck in check-in queues or on planes waiting to depart took to Twitter to share photos and frustration at the delays, as well as to ask how a major airline could be grounded by a power cut.
A Delta spokeswoman declined to comment when asked about backup systems.
The glitch follows several high-profile computer problems faced by US airlines in the past year.
Budget carrier Southwest Airlines Co had to halt departures last month after a technical outage, while American Airlines had to suspend flights from three of its hubs last September after technical problems.
Industry consultants say airlines face an increasing risk from computer disruptions as they automate more of their operations, distribute boarding passes on smartphones and fit their planes with Wi-Fi.