Complex sentence: As the longest living of the first military pilots, Foulois saw the steps into space of the Apollo Program--a direct legacy of his many career "first" milestones, and remains one of the most significant key figures in the development of U.S. air power.
Split into simpler sentences: As the longest living of the first military pilots, Foulois saw the steps into space of the Apollo Program--a direct legacy of his many career "first" milestones. He remains one of the most significant figures in the development of U.S. air power.