Travellers on Delta Air Lines are enduring hundreds more cancelled and delayed flights as the carrier battles through day two of its recovery from a global computer outage.
By early afternoon in Atlanta on Tuesday, Delta said it had cancelled about 530 flights as it moved planes and crews to "reset" its operation, while more than 1,000 are believed to have been subject to delay.
The latest disruptions follow about 1,000 cancellations and 2,800 delayed flights on Monday after a power outage at Delta's Atlanta headquarters tripped a meltdown of its booking, communications and other systems.
The airline was back online after a few hours on Monday, but the ripple effect could still be strongly felt a day later.
Dave Holtz, the airline's senior vice-president of operations, said: "We are still operating in recovery mode."
The airline has posted a video apology by CEO Ed Bastian, and has offered refunds and £150 in travel vouchers to people whose flights were cancelled or delayed by at least three hours.
Delta's challenge now will be to find enough seats on planes during the busy summer holiday season to accommodate the tens of thousands of passengers whose flights were scrubbed.
Airlines have been putting more people in each plane, so when a system of a major carrier crashes, as has happened with others before Delta, finding a new seat for those affected becomes more difficult.
Last month, the average Delta flight was 87% full.
Confusion among passengers on Monday was compounded as Delta's flight-status updates crashed as well. Instead of staying at home or poolside at a hotel until the airline could fix the mess, many passengers learned about the gridlock only after they reached the airport. By then, they were stuck.
Delta spokesman Trebor Banstetter said that after the power outage, key systems and network equipment did not switch over to back-ups. The investigation of the outage is ongoing, but he said there is no indication that the problems were caused by a hack or intentional breach of the system.
A spokesman for the local electric company, Georgia Power, said the problem started with a piece of Delta equipment called a switchgear, which direct flows within a power system. No other customers lost power, he said.
Airlines depend on huge, overlapping and complicated systems to operate flights, ticketing, boarding, airport kiosks, websites and mobile phone apps. Even brief outages can now snarl traffic and, as the Delta incident shows, those problems can go global in seconds.
Last month, Southwest Airlines cancelled more than 2,000 flights over four days after an outage that it blamed on a faulty network router. United Airlines and American Airlines both suffered outages last year - United has struggled with several meltdowns since combining technology systems with merger partner Continental Airlines.