It’s 4 days later and Delta is still affected by CrowdStrike. Here’s why.

Hundreds of Delta flights were cancelled Tuesday. Here's why the airline is still reeling from the CrowdStrike/Microsoft outages.

Most of the world has slowly recovered from the devastating CrowdStrike and Microsoft outages that hamstrung countless businesses and industries last Friday. One airline, however, is still struggling early this week.

Delta Airlines is still dealing with numerous cancelled flights and delays. It's become clear the airline has had a much more difficult time getting back on its feet than other companies across nearly all sectors of the economy.

Around midday Tuesday, more than 455 Delta flights had been cancelled, far outpacing any other airline, according to data from FlightAware. It also had more than 650 delays.

Why is Delta so slow on getting back on its feet?

Computer systems in airports, at airlines, and pretty much everywhere else went down Friday, but Delta has had unique struggles trying to recover. The issue with Delta largely stems from a crew-tracking tool that relies on Windows, leaving the airline in a difficult position as it tried to manage the overwhelming schedule changes caused by the outages.

“The technology issue occurred on the busiest travel weekend of the summer, with our booked loads exceeding 90%, limiting our re-accommodation capabilities,” Delta CEO Ed Bastian wrote in a letter to customers.

He added later in the letter:

"Specifically, the issue impacted the Microsoft Windows operating system. Delta has a significant number of applications that use that system, and in particular one of our crew tracking-related tools was affected and unable to effectively process the unprecedented number of changes triggered by the system shutdown. Our teams have been working around the clock to recover and restore full functionality."

Delta has to manually reset a ton of computers. Half its IT systems are Windows-based, which meant they crashed and need to be manually fixed after the CrowdStrike issue.

"The CrowdStrike error required Delta’s IT teams to manually repair and reboot each of the affected systems, with additional time then needed for applications to synchronize and start communicating with each other," the company said in statement.

So if you're flying Delta on Tuesday or the upcoming days, just know there's a good chance the airline is still reeling from the CrowdStrike outages.