Delta Air Lines — which now provides about 70% of departures from Salt Lake City International Airport — is serious about requiring masks on its flights.

“We’ve already banned 120 passengers from future travel with Delta for refusing to wear masks on board,” Delta CEO Ed Bastian wrote to company employees in an email Thursday.

He added that the airline just strengthened a policy requiring customers who believe that medical issues prevent them from wearing a mask to complete a “clearance-to-fly” process before they travel, including a consultation with the University of Pittsburgh Medical Center.

“And we’re encouraging those who can’t wear masks to reconsider their travel altogether,” Bastian wrote. “Countless studies and medical experts have advised us that masks are an essential response to the virus that will help us reduce transmission.”

(Francisco Kjolseth | Tribune file photo) Delta Airlines CEO Ed Bastian sits down in an interview to talk about the importance of its Salt Lake City hub, Jan. 18, 2019.

Bastian also said that the airline is working toward testing all of its employees for COVID-19 within the next four weeks.

That includes scheduling additional testing at its hubs such as Salt Lake City and introducing at-home testing for employees based elsewhere.

“By testing 100% of our people, we’re establishing a baseline that helps us make critical decisions to protect everyone’s health and safety — our employees and our customers,” Bastian wrote. “We’re exploring additional programs and technology to make it easier for everyone to stay tested, notify us if they contract the virus, and enable contact tracing to identify those who may have been exposed and reduce transmission.”

Earlier this month, Bastian also announced that at least through September, Delta will continue to block middle seats and limit its capacity on flights to 60% to allow social distancing. He also said he expects the airline will likely continue the policy even longer.

That comes after United and American airlines announced that they are discontinuing such precautions, and will fill flights to capacity — saying flying with so many empty seats is a business model that cannot be sustained. Also, the chief of United said that blocking middle seats is more of a public relations strategy than one to protect safety.

Bastian has said the future of Delta depends on it being a leader in protecting the safety of its passengers and workers, along with helping travelers to feel confidence in the airline’s priorities.