Delta Air Lines says its operations are finally getting back to normal after several days of chaos involving thousands of canceled and delayed flights that resulted from Friday's massive global IT outage that crashed millions of computers around the world.

In a statement posted to Delta's website, CEO Ed Bastian apologized for the havoc that left thousands of its travelers delayed for hours or scrambling to rebook flights said the airline expects "minimal" cancelations and delays for Wednesday, followed by a "normal day" on Thursday.

"While our initial efforts to stabilize the operations were difficult and frustratingly slow and complex, we have made good progress this week and the worst impacts of the CrowdStrike-caused outage are clearly behind us," Bastian said. He added that delays and cancellations were down 50% Tuesday compared with the day before.

Millions of Windows PCs supporting hospitals, 911 systems, banks and telecom companies, in addition to airlines and airports, crashed early Friday morning after the cybersecurity company CrowdStrike sent out a faulty update to Windows systems that crashed them and left many users staring at what's known as a "blue screen of death."

CrowdStrike said it quickly identified and fixed the problem, adding that its systems are now operating normally and that its customers remain protected from cyber threats. Mac and Linux systems weren't affected. On Wednesday, the company related a preliminary report detailing how the incident occurred as a result of an "undetected error" in the update and how it plans to prevent similar problems from happening the the future.  

"We understand the gravity of this situation and are deeply sorry for the inconvenience and disruption," the company said in a previous statement.

While the affects of the outages were widespread, the problems involving airlines, particularly Delta, were some of the most visible and longest to linger.

According to the flight-tracking website FlightAware, about 2,000 flights were canceled Tuesday, with another 33,000 delayed. About 500 of those cancelations and 1,700 of those delays involved Delta. While still significant, those numbers marked big drops from Friday's totals of more than 5,000 cancellations and 46,000 delays.

In addition to reimbursements and vouchers for meals, hotel accommodations and ground transportation, Bastian said affected Delta customers will also receive airline miles and travel vouchers as a "further gesture of apology."

That promise comes a day after the US Department of Transportation launched an investigation into Delta's response to the outage, citing a flood of complaints filed by unhappy travellers.

Transportation Secretary Pete Buttigieg announced the inquiry Tuesday morning on the social media platform X, saying that the move was being made to ensure the airline is "following the law and taking care of its passengers during continued widespread disruptions."  

"All airline passengers have the right to be treated fairly, and I will make sure that right is upheld," Buttigieg said in his post.

Buttigieg noted that Delta is required to provide prompt refunds to consumers who choose to not rebook, along with timely reimbursements for food and hotels to those affected by the delays and cancellations, as well as "adequate customer service assistance."

Customers should first try to resolve their grievances with the airline directly, Buttigieg said his department wants to hear from customers who feel Delta hasn't treated them fairly.

Delta has said it's cooperating with the investigation and remains focused on restoring its operations.