Microsoft Corporation (MSFT  ) has pointed the finger at Delta Air Lines Inc. (DAL  ) for its extended recovery from a global cyber outage.

What Happened: On Tuesday, Microsoft stated that unlike its competitors the airline's lack of IT modernization contributed to the prolonged recovery, reported Reuters.

Delta, on the other hand, defended its IT infrastructure, stating it has invested billions in IT capital expenditures since 2016.

"Delta has a long track record of investing in safe, reliable and elevated service for our customers and employees," a company spokesperson told Reuters.

Last week, Delta CEO Ed Bastian said that although the airline heavily relies on the two tech companies, they had failed to provide "exceptional service." He also said that Microsoft had the "most fragile platform."

Microsoft's lawyer, Mark Cheffo, refuted Delta's claims, stating that Microsoft's software was not the cause of the CrowdStrike incident.

He added that Microsoft had offered assistance to Delta at no charge, but the airline declined the help. Cheffo also said that Microsoft CEO Satya Nadella emailed Bastian but never received a reply.

Why It Matters: Last month, a software update by cybersecurity firm CrowdStrike Inc. (CRWD  ) triggered system issues for Microsoft customers, including many airlines. However, while disruptions subsided the next day for other major U.S. carriers, they persisted at Delta.

The airline is estimated to have lost $500 million due to the disruptions and is also facing an investigation by the U.S. Transportation Department.

Previously, CrowdStrike also denied Delta's allegations, stating that it had reached out to offer assistance but received no response from the airline. The letter also addressed Delta's consideration of legal actions, stating that the airline's threats of a lawsuit have perpetuated a "misleading narrative."