Most systems are back to normal for the many industries and businesses affected by Friday's CrowdStrike update that caused a mass outage of Microsoft Windows-run devices.

Except for Delta Airlines, where the drama appears far from over.

Related: CrowdStrike CEO Responds to Its Update Largest IT Outage in History

On Tuesday, U.S. Transportation Secretary Pete Buttigieg announced that the DOT has opened an investigation into Delta and the chaos after the outage to "ensure the airline is following the law and taking care of its passengers during continued widespread disruptions."

While you should first try to resolve issues directly with the airline, we want to hear from passengers who believe that Delta has not complied with USDOT-enforced passenger protection requirements during the recent travel disruptions. We will follow up. https://t.co/Noj5A5hE8w

Between Friday and Monday, over 1,000 flights were canceled by the airline, leaving many stranded and even more without their luggage.

As of Tuesday morning, Delta had already canceled........

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