Delta Air Lines has cancelled over 600 flights on Monday, as the global technology outage continues to cause disruptions into its fourth day. The Atlanta-based carrier had already scrapped numerous flights since Friday, when a defective software update affected computer systems worldwide, leading to widespread disruptions across airports, hospitals, and various businesses.

On Sunday alone, Delta recorded more than 1,300 cancellations and around 1,600 delays due to the ongoing technical issues. The problem was identified as a result of an update made to Microsoft Windows systems by the security firm CrowdStrike, whose software is widely used by businesses to protect against cyberattacks. Notably, only computers on the Windows operating system were affected, while systems operating on Apple and Linux remained unaffected.

Delta has faced significant criticism and complaints regarding the disruptions and customer service conditions, with Transportation Secretary Pete Buttigieg expressing dissatisfaction with the airline. He warned Delta that they will be held accountable for any passenger protection violations.

Delta CEO Ed Bastian acknowledged the significance of the issue in a blog post. He stated that the outage impacted a critical crew tracking tool, making it challenging to process the unprecedented number of changes caused by the system shutdown. Bastian assured customers that the airline's teams have been tirelessly working to restore full functionality.

The effects of the outage have been more severe for Delta compared to its competitors, as the airline cancelled 1,200 flights on Friday. United cancelled 649 flights, American scrapped 408, and Spirit cut 234 flights as a result of the global tech outage. Overall, FlightAware reported approximately 46,000 flights cancelled worldwide on Friday.

The current situation with the staffing tools at Delta has drawn comparisons to the Southwest Airlines Christmas meltdown in 2022. Southwest faced a staffing crisis and had to cancel or significantly delay about 16,900 flights, affecting the travel plans of 2 million people. The transportation department ultimately fined Southwest $140 million for its handling of the crisis.

As of Monday morning, Delta had cancelled 18 percent of its flights and delayed an additional 11 percent due to the ongoing tech outage. The airline has reached out directly to affected customers, providing apologies along with compensation options such as SkyMiles Program miles or travel vouchers. Delta is also covering certain expenses through meal vouchers, hotel accommodations, and ground transportation. Additionally, the airline has extended a travel waiver, allowing previously scheduled passengers to rebook their flights free of charge.

The Department of Transportation has stressed that Delta must inform customers of their entitlement to a refund if they choose not to travel. The DOT provides a list of each airline's customer service commitments in case of "controllable" cancellations and delays on their website, flightrights.gov.