CHICAGO (Reuters) – Delta Air Lines (DAL.N) has placed about 240 people on a “no fly list’ for failing to comply with the airline’s face mask policy, Chief Executive Ed Bastian said in a memo to employees on Thursday.

“Although rare, we continue to put passengers who refuse to follow the required face-covering rules on our no-fly list,” Bastian said in the memo, which was reviewed by Reuters.

Reporting by Tracy Rucinski