Delta Air Lines CEO Ed Bastian says the airline is facing $500 million in costs related to the global tech outage last month that disrupted emergency services, communications, and thousands of businesses. Bastian said that the monetary amount represents lost revenue as well as “the tens of millions of dollars per day in compensation and hotels” for the five-day period.

CrowdStrike blamed a bug in an update that allowed its cybersecurity systems to push bad data out to millions of customer computers, setting off the global tech outage that grounded flights, took TV broadcasts off air and disrupted banks, hospitals and retailers.

Cybersecurity company CrowdStrike also outlined measures it will take to prevent the problem from recurring, including staggering the rollout of updates, giving customers more control over when and where they occur, and providing more details about the updates that it plans.

Among airlines, Delta was by far the hardest hit hard by the outage, having to cancel thousands of flights, because key systems were crippled by the incident.

The US Department of Transportation is investigating why Delta failed to recover as quickly as other airlines. Transportation Secretary Pete Buttigieg said recently that the department would also examine Delta’s customer service, including “unacceptable” lines for assistance and reports that unaccompanied minors were stranded at airports.

Bastian said on CNBC that Delta will be seeking damages from the disruptions. CrowdStrike has not made any offers to help Delta financially so far, he added. It has offered free consulting advice.