Complex sentence: In 1974, Aérospatiale commenced development of a new medium transport helicopter based on its SA 330 Puma, the existence of the project was publicly announced at the 1975 Paris Air Show.
Split into simpler sentences: In 1974, Aérospatiale commenced development of a new medium transport helicopter based on its SA 330 Puma. The project was publicly announced at the 1975 Paris Air Show.