Complex sentence: In 1908 Santos-Dumont started working with Adolphe Clément's Clement-Bayard company to build the "Demoiselle No 19", the world's first series production aircraft.
Split into simpler sentences: In 1908 Santos-Dumont started working with Adolphe Clément's Clement-Bayard company to build the "Demoiselle No 19". It was the world's first series production aircraft.