Delta is suing CrowdStrike over a massive software glitch that caused thousands of flight cancellations

Delta Air Lines Inc. sued a cyber security firm CrowdStrike Holdings Inc. due to the chaos caused by this summer’s “disastrous” software updates which disabled millions of computers around the world and deprived most of the airline’s passenger fleet of landings.

The update failed Delta activities for several days, causing thousands of flights to be canceled and delayed, affecting more than a million customers, the airline’s lawsuit said.

CrowdStrike issued a public apology after a July 19 bug that caused computers running Microsoft Windows operating system. The outage paralyzed airports, banks, stock exchanges and businesses around the world — and proved especially difficult for Delta, which spent days trying to get its flight schedule back to normal. Since then, CrowdStrike has announced major changes to how it tests and deploys content updates.

Delta claims the botched upgrade cost the airline at least $500 million in out-of-pocket damages — in addition to “severe damage to its reputation and goodwill,” according to the complaint filed Friday in Georgia state court.

In a statement, CrowdStrike said Delta’s claims are based on misinformation that “demonstrates a lack of understanding of how modern cybersecurity works and reflects a desperate attempt to shift the blame for the slow recovery from a failure to modernize its aging IT infrastructure.”

The cybersecurity firm said it tried to reach an out-of-court settlement over the update, but “Delta chose a different path.”

Delta says the software update was “forced” on the company and not something its IT staff installed.

“These updates were sent to customers and their systems even though the customers did not enable automatic update settings,” the complaint states.

Delta’s claims against CrowdStrike include fraud, breach of contract, deceptive business practices and computer intrusion.

CrowdStrike is also facing lawsuits from investors over the failure.