Even still, Delta had a really bad time recovering, and is still cancelling flights days later. It's not just "a day or two". At a billion a week, with 30-40% cancellation rates, that's 300-400M just for this one customer. And that's just lost revenue. Imagine the extra costs: customer service complaints, hardware / IT restoration, extra wages for flight attendants working double duty to keep the remaining flights going. Madness.
Even just in travel segment, how many hotels, car rentals, uber/lyft rides, etc were cancelled b/c of missed flights? How much do you think they paid on top of the lost revenue to handle customer complaints, IT restoration, etc?
The repair costs alone at a given airport must be staggering, as every terminal screen is BSOD and needs a tech to manually restore from bitlocker.
https://www.cbsnews.com/news/delta-flight-cancellations-toda...
So, just one of the affected companies brings the total to $1B, wouldn't you say $5B is actually a low estimate?