Yesterday, a major technical outage caused Delta to ground all flights worldwide for about six hours. And though it’s been about a full day since Delta’s systems first came back online, it’s still slow going getting the airline back to where it’s supposed to be.

This morning, Delta announced it was outright canceling 250 flights today to “thin” its schedule and “reset” airline operations. Delays on flights that do operate are also expected to be widespread.

Dave Holtz, an SVP in charge of the Operations and Customer Center, said in a statement, “We were able to bring our systems back online and resume flights within a few hours yesterday, but we are still operating in recovery mode.”

Holtz added, “We are sorry for what many of our customers have experienced over the past 24 hours, including those who remain at airports and continue waiting for their flights. We are doing everything we can to return our operation to normal reliability, but we do expect additional delays and cancellations.”

In the end, Delta ended up canceling about 1000 flights yesterday, leaving passengers, crew, and planes in entirely the wrong places.

And as any traveler who’s been stuck behind something as predictable as a line of summer thunderstorms knows, any set of delays quickly cascades into a huge problem, as the virtual dominoes fall.

Not only does a backlog of stranded passengers begin to exceed the capacity of available planes, but also the crews and planes needed to make everything start working again are in the wrong places or have timed out, and need to meet a legally required rest period before they can fly again.

Yesterday the company’s CEO apologized to consumers for the failure, and vowed to get everything up and running again as quickly as possible.

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