(REUTERS) - Delta Air Lines said it was cancelling more than 500 flights worldwide on Tuesday (Aug 9) as the carrier worked to restore operations after a power outage hit its computer systems on Monday.

The company, which has not yet detailed the financial impact of the outage, said on its website that as of 12.30pm EDT (12.30am on Wednesday Singapore time), it had cancelled about 530 flights, while about 1,600 had departed. Earlier in the day, it estimated the cancellations at nearly 250.

The company said it would extend through Tuesday a waiver of fees normally collected when travellers change flights.

"Leaders and employees continue to focus on promptly moving departures at the airline's Atlanta hub, the world's busiest," Delta said.

The airline cancelled around 1,000 flights on Monday, stranding passengers at airports around the globe.

"We are still operating in recovery mode," Delta, the No. 2 US airline by passenger traffic, said on Tuesday.

Customers travelling on Tuesday should check the status of their flight at delta.com or the Fly Delta App, the company said.

Chief executive officer Ed Bastian apologised to customers on a video posted on the company's website and said Delta was working around the clock to restore its systems.

The problems arose after a switchgear, which helps control and switch power flows like a circuit breaker in a home, malfunctioned for reasons that were not immediately clear, according to Georgia Power, a Southern Co unit that provides electricity to most counties in Georgia.

Delta said it would provide US$200 (S$268) in travel vouchers to all customers who experienced a delay of more than three hours or a cancelled flight.

Shares of Delta were little changed at US$37.40 in afternoon trading.

In the past year, rivals Southwest Airlines and American Airlines Group have also suffered flight disruptions due to data system malfunctions.