Delta Air Lines will be handing out refunds and travel vouchers as penance for the latest computer malfunction to knock a major airline off stride.
The US airline cancelled more than 700 flights and had 2,600 others delayed, some for hours, after a power outage at its Atlanta headquarters caused many computer systems to crash.
The computer systems were working again a few hours later but Delta said it was still working to accommodate stranded passengers.
Its challenge on Tuesday 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 axed. Last month, the average Delta flight was 87% full.
The airline posted a video apology by CEO Ed Bastian and offered refunds and 200 dollars (€180) in travel vouchers to people whose flights were cancelled or delayed at least three hours.
An update from Delta CEO Ed Bastian: pic.twitter.com/udNN0kzbKs— Delta (@Delta) August 8, 2016
For passengers, hardship from the early morning meltdown was compounded by the fact that Delta's flight-status updates were not working either. Instead of being able to stay home, many passengers only learned about the flight problems when they arrived at the airport.
"By the time I showed up at the gate the employees were already disgruntled, and it was really difficult to get anybody to speak to me or get any information," said Ashley Roache, whose flight from Lexington, Kentucky, to New York's LaGuardia Airport was delayed.
"The company could have done a better job of explaining what was happening."
More than 1,000 people spent the night at Japan's Narita international airport when flights were cancelled.
Delta spokesman Trebor Banstetter said that after a power outage some key systems and network equipment did not switch over to back-up systems. He said the airline's investigation into the cause of the malfunction was continuing but said there were no indications of hacking.
A spokesman for Georgia Power said that the company believed a failure of Delta equipment caused the problem. He said no other customers lost power. Delta declined to comment on the power company's report.
Flights that were already in the air when the outage occurred continued to their destinations, but flights on the ground remained there.
At 7pm Eastern time, Delta said it had cancelled more than 740 flights, and tracking service FlightStats counted more than 2,600 delayed flights.
Airlines depend on huge, overlapping and complicated systems to operate flights, schedule crews and run ticketing, boarding, airport kiosks, websites and mobile phone apps. Even brief outages can snarl traffic and cause long delays.
That has afflicted airlines in the US and abroad.
Last month Southwest Airlines canceled more than 2,000 flights over four days after an outage that it blamed on a faulty network router.
United Airlines suffered a series of massive IT meltdowns after combining its technology systems with those of merger partner Continental Airlines.
Lines for British Airways at some airports have grown longer as the carrier updates its systems.
On Monday in Richmond, Virginia, Delta gate agents were writing out boarding passes by hand. In Tokyo, a dot-matrix printer was resurrected to keep track of passengers on a flight to Shanghai.
Some passengers said they were shocked that computer glitches could cause such turmoil. Others took it in stride.
Ryan Shannon, another passenger on the Lexington-to-New York flight, said passengers boarded, were asked to exit, waited about 90 minutes and then got back on the plane.
Once Delta cleared flights to take off, "we boarded and didn't have any problems. There is always a delay, or weather, or something. I travel weekly, so I'm used to it", Mr Shannon said.
Delta said customers whose flights were cancelled or delayed more than three hours could get a refund and 200 dollars in travel vouchers.
Travellers on some routes can also make a one-time change to the ticket without paying Delta's usual change fee of 200 dollars for domestic flights and up to 500 dollars (€450) for international flights.