Due to last week's global network outage, Delta Air Lines was still striving to return to normal operations on Sunday. In addition to the 3,500 flights already canceled, approximately 1,000 more flights were canceled.
The Atlanta-based airline canceled more than a quarter of its flights on Sunday and delayed another 1,700 flights, accounting for 46%, as its crew tracking system continued to be affected by the network outage, leading to ongoing operational issues.
This issue stranded thousands of Delta passengers nationwide, with some having to rent cars and drive hundreds of miles, others needing to wait days for new flights to be arranged, or simply cancel their trips.
According to FlightAware, Delta has yet to provide a timeline for a return to normal operations and has already canceled an additional 137 flights for Monday.
A software update from global cybersecurity company CrowdStrike on Friday triggered system issues for many Microsoft customers, including several airlines.
While other U.S. airlines have largely returned to normal, Delta Air Lines is still struggling to recover. United Airlines canceled 9% or 262 flights on Sunday, ranking second.
Delta Air Lines CEO Ed Bastian stated that the issue affected their Microsoft Windows systems, leading to a problem with a critical application.
Bastian said in an email to customers: "Especially affected was one of our crew tracking tools, which was unable to effectively handle the unprecedented number of changes caused by the system downtime."