American Airlines and Southwest Airlines have followed United and Delta Airlines in mandating masks for everyone except children under two years of age.

The announcements reflect a stepped-up campaign to more vigorously enforce mask-wearing during air travel, first initiated in June by the industry trade group Airlines for America.

In a statement issued July 22, American states that it will now require all customers over the age of two to wear face coverings at airports and on board. The airline said that all customers must now wear a face covering from the time they enter their departure airport and not remove it until they exit their arrival airport.

The updated policy expands American’s face covering requirement to include all areas of the airports in which American operates, including Admirals Club lounges, as well as on board all American flights and does not allow for exemptions for those over two years old.

In a statement, Alison Taylor, American’s chief customer officer, said, “Customers and team members have been clear that they feel more safe when everyone is wearing a face covering. In light of this important feedback, we are expanding and enhancing our requirements onboard and at airports.”

Customers may remove their face mask while eating or drinking. If fliers refuse to wear masks, they can be barred from future travel with the airline during the COVID-19 crisis.

Southwest Airlines has also updated its mask policy stating it is not allowing maskless travelers, with no exemptions for anyone over two years old.

“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 issued July 23. “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 airline stated that it would have masks available for customers who did not have them and that passengers were required to use them in the airport, while boarding, inflight, deplaning, retrieving baggage and at all times when engaging with Southwest employees or other customers. Passengers will be allowed to remove masks for eating and drinking but must replace them immediately afterwards.

United Airlines said this week that anyone with a medical issue needs to contact the airline prior to flying. Delta’s policy that limits medical exemptions must be proven requires that a phone call to STAT-MD, a physicans’ service hired by the airline, will be conducted before passengers are allowed to fly.