On Thursday, Bastian said in a note to customers that masks will be required on Delta through Dec. 31.
Airlines including Delta also require passengers to fill out a health acknowledgment form at check-in and agree to mask requirements during travel.
Delta is also testing its active U.S.-based employees for COVID-19 over the next four weeks, including testing at its hubs and at-home testing in Florida, Texas and other non-hub locations.
“We expect 100 percent of our people to participate,” Bastian wrote in the memo to employees. The company will use the test results for “establishing a baseline that helps us make critical decisions to protect everyone’s health and safety.”
He said Delta is looking into programs and technology for employees to more easily “stay tested,” notify the company if they contract the virus and enable contact tracing.