Most airlines —except one — are recovering from the CrowdStrike tech outage; the feds have noticed

Delta Air Lines struggled for a fourth straight day to recover from a worldwide technology outage caused by a faulty software update, stranding tens of thousands of passengers and drawing unwanted attention from the federal government.

The airline's chief executive said it would take “another couple days” before “the worst is clearly behind us.” Delta's chief information officer said Monday that the airline was still trying to fix a vital crew-scheduling program.

Other carriers were returning to nearly normal levels of service disruptions, intensifying the glare on Delta’s relatively weaker response to the outage that hit airlines, hospitals and businesses around the world.

U.S. Transportation Secretary Pete Buttigieg spoke to Delta CEO Ed Bastian on Sunday about the airline’s high number of cancellations since Friday. Buttigieg said his department had received “hundreds of complaints” about Delta, and he expects the airline to provide hotels and meals for travelers who are delayed and to issue quick refunds to customers who don’t want to be rebooked on a later flight.

“No one should be stranded at an airport overnight or stuck on hold for hours waiting to talk to a customer service agent,” Buttigieg said. He vowed to help Delta passengers by enforcing air travel consumer protection rules.

Bastian said in a video for employees that he told Buttigieg, “You do not need to remind me. I know, because we do our very best, particularly in tough times, taking care of our customers."

Delta has canceled more than 5,500 flights since the outage started early Friday morning, including at least 700 flights canceled on Monday, according to aviation- data provider Cirium. Delta and its regional affiliates accounted for about two-thirds of all cancellations worldwide Monday, including nearly all the ones in the United States.

Chicago-based United Airlines was the next-worst performer since the onset of the outage, canceling nearly 1,500 flights. United had canceled only 17 Monday flights by late morning.

Other airlines that were caught up in the first round of groundings also returned mostly to normal operations by Monday. That included American Airlines, Spirit Airlines, Frontier Airlines and Allegiant Air.

Some airlines, including Southwest and Alaska, do not use CrowdStrike, the provider of cybersecurity software whose faulty upgrade to Microsoft Windows triggered the outages. Those carriers saw relatively few cancellations.

Delta, however, said that “upward of half” its IT systems are Windows-based. The airline said the outage forced IT employees to manually repair and reboot each affected system and synchronize applications so they start working together.

“It is going to take another couple of days before we are in a position to say that ... the worst is clearly behind us," Bastian told employees Monday. “Today will be a better day than yesterday, and hopefully Tuesday and Wednesday will be that much better again.”

On the same video, Delta Chief Information Officer Rahul Samant said two applications were particularly difficult to restart on Friday: One that manages traffic at Hartsfield–Jackson Atlanta International Airport, Delta's biggest hub, and another that assigns pilots and flight attendants to flights.

Technicians had gotten the crew-scheduling program running, “but we have a catch-up to do,” and new issues keep arising, Samant said.

Atlanta-based Delta said it is offering waivers to make it easier for customers to reschedule trips.

The airline industry might be the most visible victim of the worldwide tech problems caused by the faulty software update from Texas-based cybersecurity firm CrowdStrike.

CrowdStrike said a “significant number” of the millions of computers that crashed on Friday are back in operation as its customers and regulators await a more detailed explanation of what went wrong.

A defective software update sent by CrowdStrike to its customers affected about 8.5 million machines running Microsoft's Windows operating system.

Shares of the cybersecurity company have dropped nearly 30% since the meltdown, knocking off billions of dollars in market value.

The scope of the disruptions has also caught the attention of government regulators, including antitrust enforcers, though it remains to be seen if they take action against the company.

“All too often these days, a single glitch results in a system-wide outage, affecting industries from healthcare and airlines to banks and auto-dealers,” said Lina Khan, chair of the U.S. Federal Trade Commission, in a Sunday post on the social media platform X. “Millions of people and businesses pay the price. These incidents reveal how concentration can create fragile systems.”