Instruct: Classify an Amazon review as either positive or negative.
Query: Reveals a unique aspect of American aviation

Birdflight As The Basis Of Aviation reveals a unique aspect of American aviation. Otto Lilienthal flying in a bird-wing based manually operated glider -- in the 1890s! From 1891 to his fatal gliding accident in 1986, Lilienthal did more than two thousand airborne glides and inspired the Wright Brothers to investigate human flight. The Wright Brothers cited Lilienthal as one of their heroes and carefully studied his work, developed their own theories and designs, and went on to invent the first working heavier than air aircraft. Originally published in 1889, Birdflight As The Basis Of Aviation features more than none hundred drawings, graphs, and diagrams (including many historic photographs of Lilienthal flying) and is a very welcome contribution to contemporary aviation history reference collections -- and a "must" for all American aviation history buffs.