Delta Air Lines on Wednesday made a lot of progress in getting flights back on track in its sixth day trying to recover from a technology glitch last Friday that knocked out its computer system for hours and has stranded thousands of customers ever since.

But scrutiny is growing of how the airline — the dominant carrier at Minneapolis-St. Paul International Airport — handled the situation.

CEO Ed Bastian said operations should be back to normal Thursday, after canceling nearly 7,000 flights since Friday. As of 4:15 p.m., 52 flights had been canceled Wednesday.

"While our initial efforts to stabilize the operations were difficult and frustratingly slow and complex, we have made good progress this week and the worst impacts of the CrowdStrike-caused outage are clearly behind us," Bastian said in a statement Wednesday.

Nearly 1 million passengers across the country waited in long lines, sometimes for days, trying to get new flights as the Atlanta-based carrier worked to recover after a software update by the cybersecurity firm CrowdStrike disabled computers at companies around the world.

"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 in his update. "Thursday is expected to be a normal day, with the airline fully recovered and operating at a traditional level of reliability."

At MSP, the chaos diminished significantly Wednesday, airport spokesman Jeff Lea said.

Out of roughly 980 flights — inclusive of all scheduled commercial airlines — 106 were delayed and 17 were canceled, for both arrivals and departures. Some of those delays and cancellations could have been caused by other factors, such as mechanical issues, Lea said.

"It's tremendously better from an overall view," he said.

What has yet to be determined is the impact the CrowdStrike issue will have on revenue for the Metropolitan Airports Commission (MAC), which operates MSP. The MAC is self-funded and uses rents and fees paid by airport users, not general tax dollars, to operate. Payments to the airport include landing and fuel fees.

"Could there be impact? Certainly. But at this early stage, it would have to be down the road a little bit to determine," Lea said.

Meanwhile, pressure on Delta to make sure passengers receive credits, refunds and reimbursements intensified. Federal regulators on Tuesday launched an investigation into Delta to ensure the airline lives up to its word and is complying with rules about offering compensation and refunds to passengers whose flights were canceled or significantly delayed.

And U.S. Sen. Maria Cantwell, D-Washington, who chairs the Senate Commerce Committee, wrote a letter to Bastian, telling him her committee would conduct oversight into the underlying reasons for the outage.

"While the technology outage was clearly not caused by Delta or any airline, I am nevertheless concerned that Delta is failing to meet the moment and adequately protect the needs of passengers," Cantwell wrote.

Bastian in his statement placed the blame for the airline's meltdown on CrowdStrike and said Delta has been working to fix the problems.

CrowdStrike said Wednesday in a more detailed explanation of the bug that there was an "undetected error" in the content configuration update for its Falcon cybersecurity platform affecting Windows machines.

Meanwhile, analysts are estimating that the financial impact of this week's operational meltdown on Delta will be between $350 million and $500 million, according to Bloomberg.

And customer service representatives are still trying to help passengers board new flights and get the refunds and credits due. Delta's agents are also trying to connect customers with displaced baggage across the country, though the company said Wednesday afternoon a majority of baggage claims have been resolved.

"Displaced counts are trending downward significantly as major initiatives at all Delta hubs are underway to reunite customers with bags, by ground delivery or via operating flights," the airline said Wednesday.

Delta also is trying to get crew members back to their home bases. According to a letter from a Delta pilots' union leader distributed to members Tuesday and obtained by the Star Tribune, many crew members were stranded due to the high number of cancellations.

"I share your frustration in seeing passengers stranded while we, as crew members, experience the same unacceptable obstacles we face during every IROP [irregular operation] — the inability to contact the company in any capacity and the feeling that we have been abandoned in the system," wrote Capt. Darren Hartmann, chairman of the Delta Master Executive Council, part of the Air Line Pilots Association.

In the letter, Hartmann said the chaos "will undoubtedly result in a significant number of scheduling violations, fatigue reports, and other contractual violations." Delta, however, announced it was removing the threshold at which a pilot can receive double pay for rotations between July 19 and Friday "regardless of the number of hours on their time card that apply to the [green slip] trigger."

He pleaded with pilots to adhere to fitness for duty guidelines, get adequate rest, and to notify Delta if they determine they are too fatigued during their flight duty period.

Includes reporting by the Associated Press, Atlanta Journal-Constitution and Bloomberg News.