Delta Air Lines Inc., the second-largest airline in the U.S., canceled about 275 flights on Saturday and warned that more could be scrapped after severe thunderstorms stymied travel out of the company’s largest hub this week.

The airline extended a travel waiver to help customers change flights without fees if their travel plans are flexible, according to a statement posted on the Atlanta-based company’s website on Saturday. Its biggest hub is in its headquarters city, where midweek storms have been plaguing travelers. Delta had canceled 189 flights out of Atlanta as of 11:48 a.m. local time, or about 95 percent of the airport’s total, according to data compiled by FlightAware.

“While we can’t control the weather, we understand the resulting recovery has not been ideal and we apologize for that,” Gil West, the firm’s chief operating officer, said in the note to customers. “We, as always, learn from these experiences.”

Delta has had the most cancellations of any airline since early Thursday as the airline axed about 2,000 flights in that time, according to FlightAware, following storms that hit the Southeastern U.S. and the East Coast. That compared with 207 cancellations by rival American Airlines Group Inc., the website found.

About 60 percent of Delta’s 1,250 aircraft fly through Atlanta each day, West said in an statement earlier this week. The hub accommodates “well over 150,000 people per day,” he said. The company said today that crews were still working around the clock to restore normal service.

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Photo Credit: In this Oct. 13, 2016 file photo, a Delta Air Lines jet sits at a gate at Hartsfield-Jackson Atlanta International Airport in Atlanta. Delta Air Lines says it has canceled about 3,000 flights this week as it continues to struggle in the aftermath of a storm that hit its hub airport in Atlanta. David Goldman / Associated Press