Southwest announces it will no longer allow customers without masks to fly

"If a Customer is unable to wear a face covering or mask for any reason, Southwest regrets that we will be unable to transport the individual," the airline said in a statement. "In those cases, we hope the Customer will allow us to welcome them onboard in the future, if public health guidance, or other safety-related circumstances, regarding face coverings changes."

The policy is the strictest so far among U.S. airlines.

Two other carriers, United and Delta Air Lines, have made similar changes to face covering policies. However, unlike Southwest, United and Delta may still allow some travelers to fly without wearing a face covering. Passengers flying Delta would have to undergo a separate screening process that could take more than an hour, the airline said. On United, customers will be reminded of the policy and could be denied boarding if they refuse to comply. Those with special medical conditions should contact the airline prior to their flight.

As part of a revised policy announced Wednesday, United said face coverings also would be required in all areas of the more than 360 airports it serves.

There is no federal requirement that air travelers wear masks when they fly, so airlines have largely been left to craft their own policies. A growing number of states however, are now making masks mandatory. On Wednesday, governors in Ohio, Indiana and Minnesota made face coverings a requirement.

Southwest is taking other steps to reassure travelers in the midst of a pandemic. The airline said in early August, it will launch a pilot program at Dallas Love Field to screen passengers for elevated temperatures using thermal screening cameras. The pilot program would last from 30 to 90 days, airline officials said.

"Southwest always operates a multilayered approach to supporting the well-being of travelers and employees, which is especially important during the current covid-19 pandemic," said Scott Halfmann, vice president of safety and security. "We are pleased to partner with Dallas Love Field on this pilot project as thermal screenings could be an important, additional layer of precaution that Southwest can offer customers starting at the very beginning of their travel journey."

Even with the launch of that program, the airline said it was still hopeful that the Transportation Security Administration would take on the responsibility for conducting the screenings. Southwest is among several U.S. airlines that have called on the agency to do so, given that it already conducts security screenings. However, the agency has not committed to launching such a program, saying that it is not clear that it would be effective in identifying passengers who have covid-19.

Currently, Frontier Airlines is the only U.S. airline that does temperature screenings of all passengers before they board.