Aug 8 (Reuters) - Delta Air Lines on Thursday warned of a $380 million hit to its revenue in the current quarter from operational disruptions resulting from the CrowdStrike-caused outage.

A software update last month by global cybersecurity firm CrowdStrike triggered system problems for Microsoft customers, including many airlines. The disruptions persisted at Delta even as they subsided the next day at other major U.S. carriers.

The Atlanta-based carrier canceled about 7,000 flights over five days, stranding hundreds of thousands of travelers. Delta also faces an investigation from the U.S. Transportation Department for the disruptions.

In a regulatory filing, CEO Ed Bastian said the airline has suffered a hit of at least $500 million due to the outage and is pursuing legal claims against CrowdStrike and Microsoft.

"An operational disruption of this length and magnitude is unacceptable, and our customers and employees deserve better," Bastian said.

Both CrowdStrike and Microsoft have rejected Delta's claim that they should be blamed for flight disruptions.

Microsoft this week said its preliminary review suggested that Delta, unlike its competitors, apparently had not modernized its IT infrastructure. (Reporting by Rajesh Kumar Singh in Chicago; Editing by David Gregorio)