Otto Lilienthal (1848-1896), a German inventor who made fundamental contributions to the development of heavier-than-air flight. He made over 2,000 flights in gliders of his design between 1891 and his death five years later in 1896. Fifteen of Lilienthal's gliders were monoplanes and three were biplanes. Each model was a hang glider controlled by the pilot shifting his weight rather than through the use of any active control surfaces. Lilienthal's book of aerodynamic data, Der Vogelflug als Grundlage der Fliegekunst (Birdflight as the Basis for Aviation), published in 1889, emphasized the curvature of a bird's wings as the secret of lift. Lilienthal's book greatly influenced aeronautical design and was the bible for the early designs of the Wright brothers and other early aviators.