Delta has banned 240 passengers for refusing to wear masks during flights, as it works to make flying feel safe again

• Delta Air Lines has banned about 240 passengers for refusing to wear masks during flights, CEO Ed Bastian said in a memo to employees.
• The airline said in June that it would ban uncooperative passengers, and said in late-July that it had already banned more than 100.
• The airline also strengthened its rules recently to combat phony medical exemptions.

US airlines said in June that they would begin banning passengers who refused to cooperate with on-board mask requirements — and Delta has followed through on that threat hundreds of times.

Delta has banned about 240 passengers from flying on the airline, after those passengers ignored rules and requests to wear masks during flights, CEO Ed Bastian said in a memo to staff on Thursday. The airline requires passengers to wear masks in the airport and on all flights unless they are quickly eating or drinking.

"Although rare, we continue to put passengers who refuse to follow the required face-covering rules on our no-fly list," Bastian wrote. "I want to thank everyone for your continued vigilance of our policy requiring masks be worn by our people and our customers."

The number has more than doubled over the past month — on July 22, Bastian told NBC's "Today" that about 100 passengers had been banned for mask refusal.

Among those banned in recent weeks was Robert O'Neill, the former Navy SEAL known for his part in the raid that killed Osama bin Laden.

O'Neill was on board a flight on Wednesday, August 19, when he tweeted a selfie with the caption "I'm not a p----." Unlike a fellow passenger in a US Marine Corps hat and a flight attendant visible in the photo, O'Neill was not wearing a mask. O'Neill was banned by the airline the following day.

The airline recently strengthened its mask policy, requiring anyone claiming a medical exemption to consult with a Delta-contracted telehealth medical professional before boarding.

"Any false claims of a disability or health condition to obtain an exemption from wearing a mask or face covering may result in the suspension of travel privileges on any Delta flight for the duration of the mask/face covering requirement," the airline said when it announced the plan.