The proposed rule to protect flight decks from intrusion requires aircraft manufacturers to install a second physical barrier on planes produced after the rule goes into effect and used in commercial passenger service in the United States.

"Each additional layer of safety matters. Protecting flight crews helps keep our system the safest in the world," FAA Acting Administrator Billy Nolen said.

The FAA was supposed to have adopted rules by 2019 under a 2018 federal law but the agency has said it was required to follow procedural rules before it could impose new regulations. The FAA says if finalized, the rule would apply to transport category airplanes manufactured two years after final rules are adopted.

After the hijacking of four U.S. airplanes on Sept. 11, 2001, the FAA adopted standards for flight deck security to make them resistant to forcible intrusion and unauthorized entry.

The FAA in 2007 set rules to address the flight deck security when the cockpit door was opened, including requiring the door be locked when the airplane is in operation, unless necessary to open it to permit access by authorized persons.

House Transportation Committee chair Peter DeFazio in 2019 questioned the FAA's delay, saying Congress had directed the agency to simply issue an order requiring the secondary barriers.

"Today, at most airlines, the only line of defense of the cockpit when a pilot needs to exit during flight is an improvised procedure involving flight attendants and beverage carts. This is not, and cannot be, a permanent solution," DeFazio said in 2019.

(Reporting by David Shepardson; Editing by Bernadette Baum)

By David Shepardson