The only company that - offhand - I can think of has produced both aircraft and automobiles - under the same "brand" is Ford.
Other companies that I know that have produced aircraft or engines and automobiles (again, under their own "brand") are:
BMW
Mercedes
Rolls-Royce
Packard (albeit known for its license built RR Merlin)
Messserschmitt (who can forget the post war 3-wheeler)
Mitsubishi
I don't include Siemens since although it built both engines (Siemens-Halske) and aircraft (Siemens-Schuckert), and is now a multi-industry, multi-national company, it did not build automobiles under its own name.