Delta Air Lines continued to cancel flights throughout the weekend because of the cascading effects of storms that struck Atlanta last Wednesday.

The airline said it had canceled about 150 flights on Sunday and about 275 on Saturday. It attributed its continuing troubles to difficulty staffing flights in accordance with federal rules governing how long and how often flight crews can work.

“We know this is extremely frustrating for our customers, and we apologize for that,” the airline said in a statement posted to its website on Sunday afternoon. It did not immediately respond to a request for comment on whether flights scheduled for Monday would also be affected.

The thunderstorms that descended on Atlanta on Wednesday led federal aviation officials to place a midday hold on flights into Hartsfield-Jackson Atlanta International Airport, Delta’s biggest and busiest hub. About 60 percent of Delta’s fleet travels through Atlanta on any given day.

Though the restriction was lifted hours later and the storms eventually moved on, the headaches for Delta and its customers have lingered.

The airline had already canceled thousands of flights by Friday, leading to chaotic scenes at airports. Customers affected by the cancellations and delays voiced outrage at the company in person and on social media.

Delta said that customers whose flights were canceled or delayed 90 minutes or more could request a refund. It also said that customers were allowed to change a ticket once without paying a fee.

In a statement posted online on Thursday night, Gil West, Delta’s chief operating officer, described the storm as “unprecedented” and said the airline was working overtime to address the resulting disruptions.

“Our employees are doing all they can, picking up extra flights, working overtime, and going above and beyond for our customers on the phone and in gate areas,” he said.