Delta brought its operation under control on July 24, five days after the CrowdStrike outage took out its numerous Microsoft Windows-based IT systems.
Delta has canceled 50 flights on Wednesday, or approximately 1% of its schedule, according to FlightAware. Fourteen percent of the carrier's mainline schedule had been delayed.
In a morning email to customers, CEO Ed Bastian said Delta, which is typically among the U.S. airline leaders in terms of reliability, expects to achieve a full recovery by Thursday.
"I know the last few days have been difficult. To our customers who were impacted, I want to thank you for your patience and apologize again for the disruption to your travel," Bastian wrote.
Delta and its regional subsidiary Endeavor, which operates a portion of Delta Connection-branded flights, canceled a combined 6,271 flights between July 19 and July 23, amounting to 31.6% of their schedule. The carriers delayed another 9,335 flights.
Those figures don't account for Delta Connection flights operated by Delta's contracted regional partners SkyWest and Republic Airways.
On Tuesday, the DOT announced an investigation into Delta's slow recovery from the CrowdStirke outage, focusing on whether Delta has lived up to its customer-service commitments. Amid the chaos of the operational collapse, Delta flyers endured misplaced baggage, prolonged call center hold times, and overwhelmed and faltering digital rebooking tools.
Delta has said it will issue SkyMiles points or travel vouchers to impacted customers, with amounts based on affected travel. The airline also says it will reimburse customers who have incurred hotel, meal and ground transportation expenses while in transit.
Delta has explained that its slow recovery was due to the large number of its global IT systems that rely on Windows. Last to be fixed was the airline's crew scheduling system, said Delta.