American Airlines will ban the use of face masks that have exhaust valves or vents, joining almost every major airline in the U.S. with this updated policy. Masks with valves and vents can defeat the purpose of preventing a coronavirus-infected person from spreading the virus.
American's updated policy, announced Wednesday, goes into effect Aug. 19. It states face coverings must cover the nose and mouth and cannot have exhaust valves or vents.
Valves and vents don't filter the air a person exhales, meaning larger droplets that are breathed out can escape the mask. That defeats the purpose of wearing a mask right now -- to prevent people who have the virus from giving it to others.
Alaska, Delta, JetBlue, Southwest, Spirit and United airlines also recently updated their mask policies to exclude masks with vents, valves or both as acceptable for travel.
American also says masks must be made of material that prevents the spread of respiratory droplets, so those made of mesh or lace fabrics are unacceptable.
Most major airlines are now requiring passengers -- with exceptions only for very young children -- to wear a face covering from airport to airport except when eating, drinking or taking medicine. Those who wear face shields must also wear masks. Passengers who refuse to comply may be banned from future travel on the airline.
TEGNA's VERIFY team contributed to this report.