From the wonderfully informative
www.aerofiles.com
1930: Formed as General Aviation Corp when General Motors Corp acquired Fokker Aircraft in 1929. 1930: General Aviation Mfg Co, Baltimore MD with 1930-33 acquisition of Dornier, Berliner-Joyce, Fokker, Pilgrim (American Airplane & Engine Corp) and Thaden (Pittsburgh All-Metal Aircraft Co). 1934: Became North American Aviation Inc. 1935: General Aviation officially dissolved.
North american continued to use the
J manufacturer's suffix (as in SNJ, FJ-1 etc.) until the combined designation system came along.