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

In a lawsuit Friday, Delta said the software update affected Microsoft Windows-based systems (MSFT). world has been “catastrophic” for the company, leading to days of canceled or delayed flights. Airlines predict debacle it cost 500 million dollarsalong with lost future revenue and damaged reputation.

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

Delta, which was among the hardest hit by the outage, took this legal action months later pointing with finger of the three companies. Previously, both Crowdstrike and Microsoft had criticized Delta’s handling of the situation, saying the airline had declined offers of help.

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