Delta Airlines (DAL) is suing cybersecurity company Crowdstrike Inc. (CRWD) due to a faulty software update in July that disrupted its operations and affected more than a million customers.

In a lawsuit Friday, Delta said the software update that affected Microsoft Windows Systems (MSFT) on the world was “catastrophic” for the company, leading to days of canceled or delayed flights. Airlines say the debacle it cost him $500 millionas well as loss of future income and a damaged reputation.

The complaint alleges breach of contract, gross negligence, and intentional misrepresentation or fraud by omission on the part of Crowdstrike.

Delta, which was among the companies hardest hit by the outage, filed the lawsuit after months of point a finger among the three companies. Previously, Crowdstrike and Microsoft had criticized Delta management of the situation, saying the airline had refused offers of help.

“As we sought to reach a business resolution that puts customers first, Delta chose a different path,” a CrowdStrike spokesperson told CNBC. “Delta’s claims are based on misinformation, demonstrate a lack of understanding of how modern cybersecurity works, and reflect a desperate attempt to blame its slow recovery on its failure to modernize its outdated IT infrastructure.”