The U.S. Federal Aviation Administration has proposed an airworthiness directive for certain Boeing 747-400F series airplanes that would require applying cap seals to certain fastener collars inside the fuel tanks, according to a federal government notice.

The proposed directive was prompted by a report that cap seals were not applied to certain fasteners in the fuel tanks during production and is meant to address unsafe condition on the planes, the FAA said in a Federal Register notice published on Thursday.

(Reporting by David Shepardson and Ismail Shakil; editing by Susan Heavey)