Delta has banned former Navy SEAL Robert J. O’Neill from its flights for not wearing a face mask, a source told CNBC. O'Neill gained fame for making the claim he is the shooter who killed Osama bin Laden in 2011.

Delta has a strict face mask policy that requires the coverings in all airports it serves as well as when boarding, in-flight and deplaning. The airline said it will ban anyone who does not comply with the face mask requirement throughout the pandemic while the policy is in place.

O’Neill, who told the Washington Post in 2014 he killed al-Qaeda's leader, posted a photo on Twitter that showed him on a Delta flight bound for Newark without a face mask. The photo has since been deleted.

O’Neill, who has nearly 383,000 followers, wrote a response to the selfie on Twitter that read, “I had my mask in my lap. Everyone has gone crazy.”

In a recent Twitter posting, O'Neill mocked social distancing. On Aug. 16 he posted: "With this '6 feet apart' crap, how do I find the nerd in the cafeteria?"

After his tweets about the Delta incident, O'Neill on Friday afternoon posted on Twitter: "Ex-Navy SEAL who killed Bin Laden on being banned by Delta: I’m not anti-mask."

To date, Delta has banned more than 100 people from flying during the pandemic because they violated the face mask policy. Delta does offer an exemption for fliers who have a medical condition that prevents them from wearing a face mask, but it requires a medical screening at the time of check-in to obtain the exemption.

“Part of every customer’s commitment prior to traveling on Delta is the requirement to acknowledge our updated travel policies, which includes wearing a mask,” a Delta spokesman said in a statement sent to CNBC. “Failure to comply with our mask-wearing mandate can result in losing the ability to fly Delta in the future.”

Robert O'Neill
Robert O'Neill, a former U.S. Navy SEAL, speaks in Maryville, Tennessee, Nov. 6, 2014. O'Neill, who is credited for having killed Osama bin Laden, criticized Biden's negotiations with the Taliban. Luke Sharrett/Bloomberg via Getty Images