The US transportation department said on Tuesday it was opening an investigation into Delta Air Lines after the carrier canceled more than 5,000 flights since Friday as it struggles to recover from a global cyber outage that snarled airlines worldwide. From a report:

While other carriers have been able to resume normal operations, Delta has continued to cancel hundreds of flights daily because of problems with its crew scheduling system. Since Friday Delta has been cancelling 30% or more of its flights daily through Monday, axing 444 flights on Tuesday, or 12% of its schedule as of 11.00am and delaying another 590, or 16%, according to FlightAware, after cancelling 1,150 on Monday.

The transportation secretary, Pete Buttigieg, said on Tuesday the investigation was to “ensure the airline is following the law and taking care of its passengers during continued widespread disruptions … Our department will leverage the full extent of our investigative and enforcement power to ensure the rights of Delta’s passengers are upheld.” Delta said it was in receipt of the USDOT notice of investigation and was fully cooperating. “Delta teams are working tirelessly to care for and make it right for customers impacted by delays and cancellations as we work to restore the reliable, on-time service they have come to expect from Delta,” the airline said.