Delta Air Lines sued CrowdStrike on Friday, claiming the cybersecurity company cut corners and caused a worldwide technology outage in July that led to the cancellation of thousands of flights.

The airline is seeking compensatory and punitive damages over the outage, which began when a faulty update was pushed to several million Microsoft computers. Delta said the outage disrupted its operations for several days, resulting in more than $500 million in lost revenue and extra expenses.

CrowdStrike said Delta provided “incorrect information,” did not understand cybersecurity, and tried to take responsibility for its slow recovery from the outage.

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The U.S. Department of Transportation is investigating why Delta is taking longer to recover than other carriers. Transportation Secretary Pete Buttigieg said the department would also investigate complaints about Delta customer service during the outage, including long waits for assistance and reports of unaccompanied minors stranded at airports.

Delta claims in its lawsuit that the outage occurred because CrowdStrike failed to test the update before releasing it worldwide.

Delta canceled nearly 7,000 flights over a five-day period during the busy summer vacation season. The outage also affected banks, hospitals and other businesses.

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“CrowdStrike caused a global disaster because it cut corners, took shortcuts, and circumvented the testing and certification processes it advertised for its own benefit and profit,” Delta said in the lawsuit filed in Fulton County Superior Court in Georgia. he said. close to the company’s headquarters.

A CrowdStrike spokesperson said the company was trying to resolve the dispute; One of its lawyers said in August that CrowdStrike’s liability to Delta was less than $10 million.

The spokesman said Delta’s claims were “based on misinformation, demonstrate a lack of understanding of how modern cybersecurity works, and reflect a desperate attempt to shift blame for the slow recovery away from its failure to modernize legacy IT infrastructure.”