Believe it or not there are several different uses for the letter A in Navy slang. A -- Acting (following Navy Chief's rating); e.g., CAOMA (Chief Aviation Ordnanceman Acting)

The following are all official uses for the letter A when you actually mean something other than A. Air, Allied Aviation Corporation manufacturer's symbol, Amphibious plane as in PBY-6A, Army, Arresting Gear as in SOC-3A, Asiatic, Auxiliary, 3-drum, express type (boiler), Brewster Aeronautical Corporation manufacturer's symbol, Noorduyn Aviation, Ltd. manufacturer's symbol, Plane built for Army Air Forces suffix to plane designation as in SBD-3A, and finally USNR officer designation for General Service, Aviation Non-flying, formerly (A).

Most of these are no longer used within the Navy, but it goes to show you how inventive sailors can be.