New York CNN Business  — 

Dozens of people have been barred from flying on Delta airplanes for refusing to comply with the airline industry’s mask policies, Delta CEO Ed Bastian told CNN’s Julia Chatterley on Friday.

“We’ve had well over 100 people that have refused to keep their mask on during the flight,” he added.

A spokesperson confirmed to CNN Business that those people have lost the ability to book future flights on Delta.

Delta, along with other major US carriers, warned in mid-June that airlines would begin banning passengers who refuse to wear masks during air travel in an effort to beef up enforcement of the policy. The federal government has not made mask-wearing a mandate, leaving it up to airlines to enforce their own policies.

The carrier has put in place some of the strictest pandemic-related policies in the industry, including requiring health screenings for passengers who cannot wear masks and pledging to leave middle seats empty to put distance between travelers.

Bastian said in a separate interview with CNN last month that the vast majority of Delta passengers are compliant. But the customers who are not have caused disruptions.

Last week, for example, a Delta flight taking off from Detroit was forced to return to the gate when two of their customers refused to wear masks, the airline said.

“You can’t get on the plane without wearing your mask. But we do have some customers that don’t want to keep their mask on during flight,” Bastian said Friday. “We remind them several times over the course of getting ready to take off to please keep that mask on. But if they insist upon not wearing it — we insist that they’re not going to travel on Delta today.”

Bastian has made a focus on health-related policies a core part of Delta’s response to the pandemic.

In a note to employees on Thursday, the CEO reiterated that boosting customer satisfaction and assuring passengers of their safety is a key part of Delta’s current business strategy: “We want to ensure that those who travel now are choosing Delta.”

That “will help bring in the additional revenue we need to reduce our cash burn,” the letter reads. “It also will build additional loyalty and affinity for our brand, which will power our growth when demand begins to come back.”