In 1993, the FAA issued a combined bulletin that clarified that jump planes can carry a number of skydivers that may exceed the number of seats or passengers than that stated by the aircraft’s type design certificate, as long as weight and balance limits are observed. Though the bulletins carry an expiration date, technically the information does not expire and has been incorporated within FAA policy. These bulletins were FSAW 93-09 (Flight Standards Information Bulletin for Airworthiness) and FSGA 93-02 (Flight Standards Information Bulletin for General Aviation).
Download bulletin for Airworthiness and General Aviation.