The Delta Air Lines travel meltdown tied to CrowdStrike's global outage has turned into a blame game.

Microsoft, CrowdStrike and Delta have all pointed the finger at someone else, creating confusion among the public over what actually happened.

CrowdStrike's July 19 outage, caused by a "defect found in a single content update for Windows hosts," impacted every major airline. But while rival carriers were able to swiftly get back up and running within a day or two, problems at Delta lasted for nearly a week, prompting an investigation by the Transportation Department. 

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Now, a legal battle is unfolding between CrowdStrike and Delta as the airline attempts to recover costs lost during the outage. 

Delta Air Lines CEO Ed Bastian previously told staff that the company informed Microsoft and alerted CrowdStrike and Microsoft it was pursuing legal claims against the companies to recover losses caused by the outage, which it pegged at half a billion dollars. 

In an interview with CNBC's "Squawk Box," Bastian said the company had "no choice" given that it took a hit from lost revenue as well as compensation and hotel costs for displaced passengers. Bastian pegged the negative impact that the carrier faced at "half a billion dollars in five days."

A source confirmed to FOX Business Delta has hired prominent attorney David Boies, chairman of Boies Schiller Flexner, to pursue possible damages from CrowdStrike and Microsoft. The news was first reported by CNBC. 

Delta Chief Information Officer Rahul Samant explained in an internal video that problems persisted for so long because 60% of the "most critical applications that run the airline" are on Microsoft Windows. This meant that "all of them were rendered inoperable early on Friday, and it took us a few hours to manually touch each one of those to get the bug out and get them back on their feet," he continued. 

Bastian also claimed during an interview on CNBC that CrowdStrike only offered "free consulting advice to help us."

Delta told FOX Business in a statement Wednesday that it has invested "billions of dollars in IT capital expenditures, in addition to the billions spent annually in IT operating costs," since 2016.

In a letter to Delta's lawyers, Mark S. Cheffo, co-chair of Dechert's global litigation practice, asserted that Microsoft’s software had not caused the CrowdStrike incident but even still, "Microsoft immediately jumped in and offered to assist Delta at no charge." 

Cheffo further noted that Microsoft employees repeated their offers to help Delta "each day that followed" from July 19 through July 23. However, "each time, Delta turned down Microsoft’s offers to help, even though Microsoft would not have charged Delta for this assistance," he continued. 

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On July 22, a Microsoft employee allegedly messaged a Delta employee: "just checking in and no pressure to reply, but if you can think of anything your Microsoft team can be helping with today, just say the word." The Delta employee, according to the letter, replied saying they were "all good."

"Microsoft empathizes with Delta and its customers regarding the impact of the CrowdStrike incident," Cheffo said. "But your letter and Delta’s public comments are incomplete, false, misleading, and damaging to Microsoft and its reputation." 

In the letter, Cheffo also told Delta lawyers that the carrier "likely refused Microsoft’s help because the IT system it was most having trouble restoring—its crew-tracking and scheduling system—was being serviced by other technology providers, such as IBM, because it runs on those providers’ systems, and not Microsoft Windows or Azure." 

IBM has not yet returned Fox Business' multiple calls and emails for comment. 

Similarly, Michael Carlinsky, CrowdStrike lawyer and co-managing partner at Quinn Emanuel Urquhart & Sullivan, also wrote a letter to Delta's lawyers saying the carrier refused onsite assistance from CrowdStrike.

"Within hours of the incident, CrowdStrike reached out to Delta to offer assistance and ensure Delta was aware of an available remediation" and that its CEO, George Kurtz, personally reached out to Delta CEO Ed Bastian "to offer onsite assistance, but received no response," Carlinsky said. 

When CrowdStrike followed up with Delta on the offer of onsite support, it was told "resources were not needed," Carlinsky continued. 

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CrowdStrike's lawyers are arguing that Delta’s public threat of litigation has "contributed to a misleading narrative that CrowdStrike is responsible for Delta’s IT decisions and response to the outage." 

CrowdStrike and Microsoft declined to comment further beyond the letters. 

A spokesperson for CrowdStrike told Fox Business that the company has expressed our regret and apologies to its customers for this incident but that "public posturing about potentially bringing a meritless lawsuit against CrowdStrike as a long-time partner is not constructive to any party." 

The U.S. Department of Transportation’s Office of Aviation Consumer Protection is investigating the carrier following continued widespread flight disruptions and reports of customer service failures. 

The department said this process will continue to evolve as it learns more and processes the high volume of consumer complaints we have already received against Delta.

In a statement to FOX Business, DOT Secretary Pete Buttigieg said Delta "must take care of their passengers and honor their customer service commitments." 

Buttigieg added that: "This is not just the right thing to do, it’s the law, and our department will leverage the full extent of our investigative and enforcement power to ensure the rights of Delta’s passengers are upheld."