Bart Jansen

USA TODAY

British Airways said Sunday that it was recovering from a technology failure, but the carrier was still hobbled by the cancellation and delays of hundreds of flights at London's airports during the holiday weekend.

“We expect some further disruption today, but we are aiming to operate the majority of services from Heathrow and a near-normal schedule at Gatwick,” the airline said Sunday in a statement at 9:30 a.m.

“Please do not come to the airports unless you have a confirmed booking for travel. At this time, we are unable to process rebookings at airport terminals.”

British Airways canceled 143 flights and had 381 flight delays by 4 p.m. Sunday, according to FlightAware.com, an online tracking service. The airline previously canceled 408 flights and had 226 delays on Saturday.

The airline offered customers a full refund with the option to rebook for future travel by November. A significant amount of luggage has piled up at Heathrow, but the airline said it would be returned to passengers “as soon as we can” free of charge.

“We are extremely sorry for the significant levels of disruption caused to customers and understand how frustrating their experiences have been,” the airline said.

Passengers faced long waits to see whether they could fly; some slept at the airports.

“Everyone is upset. There are people in tears,” Melanie Ware, who flew in from Los Angeles and was trying to get to Venice on her honeymoon, told Sky News. “We rebooked for Venice for tonight, which they also have canceled now. So we have no way of getting out of Heathrow, and they haven’t compensated us for anything. And we’re stuck, and this is the worst honeymoon ever.”

The airline blamed the outage on a power-supply problem on a weekend with a Monday that is a spring bank holiday in England and Memorial Day in the U.S.

“I know this is a horrible time for customers,” BA CEO Alex Cruz said in a video statement as he apologized for the disruptions.

He said Gatwick was at nearly full operation "though some flights may be subject to delays." The airline planned to fly all of its long-haul flights from Heathrow, with some delays; short-haul flights would see some cancellations and delays.

The low-cost competitor Ryanair tweaked its larger rival in a tweet that suggested passengers should have flown a different carrier.

Many passengers complained about a lack of information from the airline.

“Some 80-year-old lady was standing around waiting for announcements, etc., and she fell over,” said Terry Page of London, who managed to get on one of the last flights from Heathrow to Dallas-Fort Worth on Saturday.

“We helped her up and she said ‘I’m just so tired,’” said Page, whose luggage didn’t arrive in Texas with him. “It’s been a terrible, terrible day.”

Contributing: The Associated Press