Delta Air Lines, which has axed more than 6,000 flights since a widespread IT system failure on Friday, said it would resume normal operations Thursday.
The Atlanta-based carrier as of 8 a.m. ET (1200 GMT) had canceled just 47 of Wednesday's flights - only 1% of its daily total - after scrapping 511 on Tuesday and 1,160 on Monday.
CEO Ed Bastian said in a statement that Delta expected "minimal" cancellations Wednesday and a return to normal operations Thursday, adding: "Our initial efforts to stabilize the operations were difficult and frustratingly slow and complex."
A software update by global cybersecurity firm CrowdStrike triggered system problems for Microsoft customers, including many airlines, on Friday. But disruptions subsided the next day at other major U.S. carriers while persisting at Delta.
The U.S. Transportation Department opened an investigation Tuesday into the Delta disruptions, which affected more than 500,000 passengers and stranded people across the United States.
Transportation Secretary Pete Buttigieg said the investigation is focused on how the breakdown happened, why it had taken Delta so much longer than others to recover, and the level of Delta's customer service resources.
"We require a basic level of customer service," he added.
Many customers complained of waiting hours for assistance as the airline's helplines were overwhelmed. Some were forced to rent cars, driving hundreds of miles to get to destinations, while others said they would have to wait days for new flights.
Representative Rick Larsen, the top Democrat on the House Transportation Committee, said he will introduce legislation to boost the operational resilience of airlines in the near future. "The slow response by some airlines to this meltdown has been unacceptable," Larsen said.
Senate Commerce Committee chair Maria Cantwell said she is concerned Delta is not complying with passenger rights obligations under a new law.
In December, Southwest Airlines agreed to a record $140 million civil penalty over a 2022 holiday meltdown that led to 16,900 flight cancellations and stranded 2 million passengers, resolving a U.S. Department of Transportation investigation.
