Complex sentence: W. A. Eddy himself demonstrated this when he was remained in the air for over 15 hours using nine Malay kites tied together by a two mile long cord, reaching, at his highest point, over 5,595 feet (1,705 m) in altitude.
Split into simpler sentences: W. A. Eddy himself demonstrated this when he remained suspended in the air for approximately 15 hours. Ssing nine Malay kites tied together by a two mile long cord, Eddy reached--at his highest point--somewhere around 5,595 feet (1,705 m) in altitude.