Microsoft on Tuesday criticized Delta Airlines after it struggled for days to recover from a global cyber outage that caused the cancellation of more than 6,000 flights.
The flight disruptions left hundreds of thousands of travelers stranded and cost Atlanta-based airlines an estimated $500 million in losses.
Delta CEO Ed Bastian told CNBC last week that the airline relies heavily on Microsoft and CrowdStrike, but that the tech companies have failed to provide “great service.”
In the interview, he also said that Microsoft has the “most vulnerable platform.”
Microsoft said it is still investigating the circumstances surrounding the CrowdStrike incident to understand why other airlines, including American Airlines and United Airlines, were able to fully restore operations much faster than Delta.
But the company added that a preliminary investigation showed that Delta appeared to have not modernized its IT infrastructure like its competitors.
In a letter from its outside counsel, the company said the airline’s comments were “incomplete, false and misleading and are damaging to Microsoft and its reputation.”
Microsoft said its employees offered Delta multiple times to help after the outage, but the airline declined.
The tech giant said CEO Satya Nadella had emailed Bastian but did not receive a response.
The airline accused Delta of using the services of another technology provider for its crew tracking and scheduling system, arguing that this was likely the reason for its refusal to help.
Delta Air Lines was not immediately available for comment.
CrowdStrike also denied Delta’s claims that the flight disruptions were to blame.
