(Reuters) - Major airlines want the Federal Aviation Administration to delay a requirement set to take effect in August requiring that new passenger airplanes have a secondary barrier to the flight deck to prevent intrusions, the agency said on Tuesday.

Airlines for America, the trade group representing American Airlines , United Airlines , Delta Air Lines and other major carriers, said the FAA should delay the requirement finalized in 2023 because the agency has not yet approved a secondary cockpit barrier and no manuals, procedures or training programs have been authorized.

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.