(1) Mechanics will be rated as airframe or powerplant mechanics.
(2) A person may hold a plurality of certificate of competency, including both classes of mechanic's certificate of competency or a pilot's and mechanic's certificate of competency.
(3) The certificate shall be a currently effective certificate of competency issued by the government of the United States.
(4) This restriction does not apply to mechanics employed by the United States government.