Southwest Airlines on Wednesday announced what is arguably the most restrictive rule yet on face coverings: all passengers over the age of two must wear one -- no exceptions.
"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."
Studies have found some people who have COVID-19 may not show symptoms right away or at all, which is why people who don't feel ill are also urged to wear masks.
Southwest says the mask must cover both the nose and mouth. The policy goes into effect Monday.
Major U.S. airlines have adopted a policy of requiring masks or coverings from gate to gate. They have generally allowed for restrictions for people who are unable to wear a mask for medical reasons and for young children. They also allow masks to be removed in flight for eating, drinking or taking medicine.
But that has led to numerous instances of people claiming a medical exemption and insisting they can't wear one. In many cases, it results in them being removed from the plane. Social media videos have shown some do not go quietly.
Some airlines have instituted policies of saying passengers who refuse to wear masks will not be allowed to fly with them again until guidance about masks from the Centers for Disease Control and Prevention or other experts changes.
Delta Air Lines last week revealed that passengers who request a medical exemption will have to undergo a private evaluation by phone with the carrier's in-flight medical partner, STAT-MD. It warned that any false claims made to obtain an exemption may result in the suspension of travel privileges on Delta.
Delta CEO Ed Bastian told NBC's Today show Wednesday that it has put more than 100 people on a list of passengers banned from flying for refusal to wear a mask.
While most people who contract the coronavirus recover after suffering only mild to moderate symptoms, it can be deadly for older patients and those with other health problems.
The Associated Press contributed to this report.