Delta Airlines expressed its frustration with CrowdStrike in a new letter on Thursday as the two companies continue to trade blows following last month’s global network outage.
The US airline accused the cybersecurity company of “negligence” and said it had had to cancel thousands of flights as a result, losing at least $500 million (£392 million).
CrowdStrike had denied that it was solely responsible for the disruptions to Delta’s flight operations, which it said continued even after other airlines were back online.
Delta has since faced a class action lawsuit filed on behalf of affected passengers.
The global bug originated on July 19 from CrowdStrike after the company sent a corrupted software update to its customers.
Microsoft estimates that 8.5 million Windows devices were disabled worldwide as a result.
Delta Airlines’ operations were disrupted for days, while other airlines appeared to have recovered. Around 7,000 flights were canceled on five days up to July 24. The U.S. Department of Transportation will now investigate the airline because of the disruptions.
The airline blamed CrowdStrike and Microsoft for the disruptions and threatened legal action. Both companies denied the accusation that they were responsible.
Delta CEO Ed Bastian wrote in a letter to the U.S. Securities and Exchange Commission (SEC) on Thursday that what happened was “unacceptable.”
“Our customers and employees deserve better,” Bastian wrote, adding that the technology breakdown affected 1.3 million Delta customers.
CrowdStrike said on Sunday that the company would defend itself “aggressively” if Delta took legal action against the company.
Microsoft also announced a fightback, adding that a preliminary investigation shows that Delta, unlike its competitors, is working with an outdated IT infrastructure.
In response, David Boies, a lawyer for Delta, wrote in a letter to CrowdStrike on Thursday: “There is no basis – none whatsoever – to believe that Delta was in any way responsible for the faulty software that caused systems around the world to crash.”
He added that Delta Airlines has invested billions of dollars in its technology and said its dependence on Microsoft and CrowdStrike has made it difficult to resume operations.
CrowdStrike accused Delta of spreading “a misleading narrative.”
A lawsuit has also been filed against Delta on behalf of passengers whose flights were canceled.
The lawsuit stated that “no other U.S. airline has canceled even a tenth as many flights.”
It was also alleged that Delta did not adequately compensate passengers and asked them to sign waivers releasing Delta from all legal claims.
Many airlines rely on Microsoft Office 365 for flight planning. The CrowdStrike outage crashed these systems, forcing companies to resort to manual planning.
CrowdStrike has since been sued by its shareholders, who accused the company of making “false and misleading” statements about its software testing. CrowdStrike has denied the allegations.
