The technical issues stem from an update issued for systems that run on Microsoft Windows by the security firm CrowdStrike, whose software is widely used by businesses seeking to defend themselves against hackers. The problems Friday affected only computers using the Windows operating system, CrowdStrike said, leaving Apple- and Linux-run operating systems unaffected.
Delta has been the subject of hundreds of complaints filed with the U.S. Transportation Department over “continued disruptions and unacceptable customer service conditions,” according to a social media post Sunday from Transportation Secretary Pete Buttigieg.
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“I have made clear to Delta that we will hold them to all applicable passenger protections,” Buttigieg said.
In a Sunday blog post, Delta CEO Ed Bastian said that the outage had affected an important tool related to crew tracking and that it was 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,” Bastian wrote.
The outage has taken a bigger toll on Delta than its rivals. It scrubbed 1,200 flights Friday, while United Airlines canceled 649 flights, American Airlines scrapped 408 and Spirit Airlines cut 234. All told, there were about 46,000 flights canceled worldwide Friday, according to FlightAware.
As of midafternoon Monday, the number of total worldwide cancellations had fallen to about 1,500. The Transportation Department said in a statement that airlines aside from Delta have “largely been able to recover.”
Some health-care organizations also saw a return to normal after having to put off procedures Friday. Mass General Brigham, a Boston-based hospital, said Sunday that it was “fully operational and open to patients” and had resumed its normal clinical volume.
At Trinity Health, a nonprofit health-care system that operates in 27 states, only a small percentage of servers were affected, and all had been fixed by Friday afternoon, a spokesperson said in an email Monday. Providence, another large health-care system, said its operations were “nearing normal levels” to start the week, although some clinics could continue to see delays, a spokesperson said.
Errol Weiss, chief security officer at the information security group Health-ISAC, told The Washington Post that around half of all hospitals use CrowdStrike, and 20 percent of those were still having problems Monday afternoon.
Windows-controlled medical devices, medical records, pharmacy orders and more were affected, he noted, adding that more and more hospitals had installed CrowdStrike in the past few years because of the devastation wreaked by ransomware gangs.
The problems with airline staffing tools drew comparisons to the 2022 Christmas meltdown at Southwest Airlines, which canceled or significantly delayed about 16,900 flights, disrupting the travel plans of 2 million people, according to a Transportation Department investigation. In that case, a winter storm spiraled into a broader staffing crisis as the airline’s system for matching crew members with aircraft couldn’t keep up.
The agency ultimately fined Southwest $140 million over its handling of the crisis.
Delta said Monday that it had communicated directly with customers, offering them an apology along with SkyMiles program miles or a travel voucher. It also offered to cover certain expenses through meal vouchers, hotel accommodations and ground transportation. Additionally, the carrier extended a travel waiver allowing previously scheduled fliers to rebook their flights free.
The Transportation Department has emphasized that Delta must inform its customers that they are entitled to a refund if they choose not to travel.
The department lists each airline’s customer service commitments in the event of “controllable” cancellations and delays on the website flightrights.gov.
Joseph Menn and Daniel Gilbert contributed to this report.