The CrowdStrike outage cost Delta $500 million, CEO Ed Bastian said during a Wednesday interview on CNBC.
That includes tens of millions of dollars in compensation to customers as well as lost revenue.
The July 19 CrowdStrike software update failure resulted in more than 6,300 cancellations between Delta and its regional subsidiary Endeavour over the following five days.
Bastian called the outage a wake-up call, but he didn't offer potential steps to make the carrier less vulnerable to third-party IT in the future. Delta has made hundreds of millions of dollars of investments in redundancies he said, but it suffered the most from the CrowdStrike failure because it is the airline most reliant on both CrowdStrike and Microsoft, whose Windows operating systems were impacted by the outage.
He added that Delta had to reset 40,000 servers over the course of its recovery.
"How do you rethink the fortification? We thought we had the best between Microsoft and CrowdStrike," Bastian said.
The airline, he said, will have no choice to sue for the damages the outage caused.
The DOT has said it is investigating Delta for potential failures to meet its customer service commitments and obligations during the five-day operational collapse that followed the CrowdStrike failure.