Delta faces a DOT investigation as its operational crisis reaches Day 5, resulting in 5,000 flight cancellations.

Check for the latest updates here: Delta reports progress in restoring operations, but many questions linger.

The Biden administration has initiated an inquiry into Delta Air Lines as the airline's operational crisis extends into a fifth day, marked by widespread cancellations following a global IT outage last Friday.

The U.S. Department of Transportation's Office of Aviation Consumer Protections is investigating the airline's "ongoing extensive flight disruptions" and "alarming customer service complaints," the agency announced on Tuesday.

This comes as the Atlanta-based airline has been canceling over 1,100 flights each day for four consecutive days, from Friday to Monday.

As of 10:30 a.m. EDT on Tuesday, Delta had already scrapped 442 more flights, representing approximately 12% of its operations, according to data from FlightAware. Cancellation numbers have increased throughout the day, raising concerns for travelers on Tuesday.

The widespread disruptions have created chaotic situations at airports nationwide, especially at Delta's primary hub, Hartsfield-Jackson Atlanta International Airport (ATL).

Frustrated travelers, lengthy lines for customer service, and scenes of passengers resting on the floors of airport concourses have become all too common in recent days.

"We have made it clear to Delta that they must prioritize their passengers and uphold their customer service promises," stated Transportation Secretary Pete Buttigieg during the announcement of the investigation on Tuesday, which "will continue to develop" as the department handles a significant number of consumer complaints.

A number of U.S. airlines, along with many international carriers, were impacted by Friday's IT issue at Austin-based CrowdStrike, which created significant challenges for Microsoft clients.

Nevertheless, Delta's difficulties have intensified even as other U.S. airlines have started to recover.

According to FlightAware data, Delta has canceled over 5,000 flights since Friday, with its cancellation rate consistently exceeding 30% in recent days, a stark contrast to the mere 0.3% of flights it had previously canceled in 2024.

Issues with the crew scheduling system

In a Monday update, CEO Ed Bastian revealed that nearly half of the airline's global IT systems run on Windows, necessitating manual repairs and reboots for each machine, along with additional time for applications to sync and communicate effectively.

Delta highlights significant issues with its essential crew-scheduling system, which is crucial for positioning crews correctly and on time.

U.S. travelers are acutely aware of how crew scheduling software failures can disrupt air travel. For instance, Southwest Airlines' holiday meltdown in 2022 was largely intensified by its crew scheduling issues, leading to nearly 17,000 cancellations after a winter storm in December just before Christmas.

"This system is vital because it ensures that the aircraft, cabin crew, and flight crew are all in the right place at the right time to maintain the flight schedule," stated Michael McCormick, a veteran of the Federal Aviation Administration.

"When the system fails... manual planning becomes necessary," he noted. "This involves a flurry of emails, texts, and phone calls throughout the system to manage it effectively."

Is a vulnerability revealed?

According to McCormick, now part of the faculty at Embry-Riddle Aeronautical University, this recent outage and the chaos it caused should act as a crucial wake-up call for airlines.

"This situation underscores the necessity for improved firewalls, emphasizing cybersecurity, along with the need for redundancy and backup systems," McCormick stated. "Airlines have become heavily reliant on automation, and as we have seen — and continue to witness — they cannot manage their flight schedules without it."

Delta's response

Delta has announced that it is offering affected travelers the choice of flight credits for future travel or cash refunds for eligible passengers. Refund requests can be submitted at delta.com/refund.

The airline also mentions that it is providing meals, hotel accommodations, and ground transportation for stranded passengers, as detailed on the Airline Customer Service Dashboard.

Meanwhile, Delta employees are working "around the clock" to restore operations, as CEO Ed Bastian mentioned in a video message to staff on Monday — a message that left some uncertainty regarding when these issues might be resolved.

"Continue to provide excellent care for our customers and support each other in the coming days," Bastian urged.