Delta Air Lines continued to struggle to restore its operations on Monday, three days after a global IT outage snarled flights around the world, stranding thousands of customers across the country.
The Atlanta-based airline had cancelled 778 flights, or about 20 percent of the scheduled total as of 1:30 pm EST on Monday, according to data from FlightAware. It accounted for about half of total flight cancellations.
By contrast, disruptions at other major US carriers had largely subsided.
A software update by global cyber security firm CrowdStrike triggered system problems for Microsoft customers, including many airlines, on Friday.
A Delta spokesperson did not immediately respond to requests for comment.
Delta CEO Ed Bastian said over the weekend the outage affected one of its crew tracking tools and the airline was "unable to effectively process the unprecedented number of changes triggered by the system shutdown."
In a separate note, he told employees that Delta would continue to "tactically adjust" schedules to ensure safety.
Delta is widely respected for running a reliable operation. Analysts say its on-time performance in terms of arrivals and departures has helped the airline cement its position as a premium airline.
Since the outage, it has cancelled nearly 30 percent of its flights, according to global aviation analytics firm Cirium.
The issue has left customers fuming. Many complained that they had to wait hours for assistance as the airline's helplines were overwhelmed.
Some were forced to rent cars to drive hundreds of miles, while others said they would have to wait days for new flights.
"I was very disappointed in the way Delta handled this," wrote Bob Pearlman on LinkedIn, who had booked a flight from Honolulu to Salt Lake City.
Bastian said the outage hit the airline on "the busiest travel weekend of the summer," limiting its re-accommodation capabilities.
In a staff memo seen by Reuters, Delta said it is "doing everything possible" to bring stability to its staffing. It has boosted incentive pay for pilots and flight attendants.
"The single biggest thing you can do to help at this point is to pick up trips in any base," it said in the memo, a request for crew to volunteer for extra trips.
US transportation secretary Pete Buttigieg said his office had received hundreds of complaints about Delta's customer service and asked the airline to provide prompt refunds, free rebooking and timely reimbursements to customers.
"No one should be stranded at an airport overnight or stuck on hold for hours waiting to talk to a customer service agent," he said.
