This story was updated at 3:30 p.m. Eastern on July 20, 2024.

More than 24 hours after a security update on computers running the Microsoft Windows operating system caused a massive global outage, air travelers in the U.S. are looking at a second day of disruption.

On Friday, American travelers saw nearly 13,000 flight delays and 3,400 cancellations, according to data from FlightAware. All told, roughly 60% of all flights departing from U.S. airports Friday were disrupted.

As of 3:30 p.m. Eastern Time on Saturday, there were 1,621 canceled flights in the U.S. and 4,945 delays, according to data from FlightAware. In effect, roughly 28% of all flights departing from U.S. airports Saturday are facing disruption for the day.

Forbes2,600 Canceled U.S. Flights And Climbing Due To Global OutageBy Suzanne Rowan Kelleher

Delta and United Airlines have been hit the hardest with 811 and 378 cancellations, respectively, on Saturday.

“The high cancellation rates by Delta and United today is likely an attempt to return their operating schedule to normal operations as quickly as possible,” says a spokesperson from Cirium, an aviation analytics company, noting that as Australia has ended its Saturday with more than 5% of its flights being canceled. “That gives an indication of where things are headed for the U.S. and Canada in particular.”

The five U.S. airports with the most cancellations on Saturday morning were Atlanta’s Hartsfield-Jackson (219), Denver (55), Chicago O’Hare (52), Minneapolis/St. Paul (51) and Detroit Metro Wayne County (51).

On Saturday, the Federal Aviation Administration (FAA) responded to an update request by directing Forbes to the agency’s website, which still carried a statement from Friday: “The FAA is closely monitoring a technical issue impacting IT systems at U.S. airlines. Several airlines have requested FAA assistance with ground stops for their fleets until the issue is resolved.”

The most-impacted airlines are issuing waivers, allowing passengers traveling Friday to rebook their flights at no extra charge.

The FlightFinder tool on FlightAware can give travelers an early heads-up of a flight disruption. Enter your flight information, and then click the “Where is my plane now?” link just under the flight number. You’ll be able to see if the plane is ahead of schedule, on time or behind schedule and you can act accordingly — even before the airline announces a delay or cancellation.

“Although this incident is beyond the control of airlines and airports, passengers still have certain rights under U.S. Department of Transportation (DOT) regulations,” says Tomasz Pawliszyn, CEO of AirHelp, an online service that helps air passengers get compensation from airlines when flights are canceled, delayed, or overbooked. “Passengers are entitled to assistance from the airline. This can include rebooking on the next available flight and, in some cases, meal vouchers and accommodation if the delay extends overnight.”

Pawliszyn’s advice: Save your receipts.