Delta (DAL), United (UAL), and American Airlines (AAL) are now requiring all travelers to wear face masks or face coverings when flying, effective May 4.

Delta said the measure adds an "extra layer of protection" for both customers and employees as its workers will also be wearing face masks when they are unable to maintain six feet of distance from another person.

Face coverings will be required at check-in, in Delta Sky Clubs, at the boarding gate, on jet bridges, and onboard the aircraft, except during meal service. Children that are unable to wear a face mask are exempt from the requirement.

Delta said it encourages travelers to bring their own face mask, but said it will have supplies available to those customers that need them.

"Nothing is more important than the health and safety of our people and our customers," Bill Lentsch, chief customer experience officer, said in a statement. "While we remain committed to our new standard of clean and to providing more space for our customers when they travel, we take seriously the CDC guidelines for adding this extra layer of protection. We believe this change will give customers and employees some additional comfort when traveling with us."

United has also enacted a face-covering requirement during the coronavirus pandemic and will make it mandatory to wear a face mask when traveling with the airline. The company’s employees are also required to wear face masks when working. United said it will have them available for free to customers.

American Airlines is also making face masks a requirement onboard its aircraft in response to the COVID-19 pandemic. The airline said very young passengers and those with health conditions that prevent them from wearing a mask will be exempt from the requirement.

American’s flight attendants will also be required to wear a face mask, starting on Friday.

"The American Airlines team continues to prioritize the safety of our customers and team members, and requiring a face covering is one more way we can protect those on our aircraft," Kurt Stache, senior vice president of Customer Experience, said in a statement. "We ask customers to bring their own masks or face coverings they’re comfortable with when they travel. American is working to procure face masks and hand sanitizer as a supplement."

Shares of Delta stock were down 5.81% as of 11:14 a.m. EDT on Friday while shares of United stock were down 7.30% at the same times. Shares of American stock were down 7.83% also at the same time.

Airlines for America represents American Airlines, United Airlines, Delta Air Lines and Southwest Airlines as well as shippers FedEx and UPS
Airlines for America represents American Airlines, United Airlines, Delta Air Lines and Southwest Airlines as well as shippers FedEx and UPS AFP / PEDRO PARDO