airplane brushed the ground over a distance of 160 ft. Inventors continued to pursue the dream of sustained flight. Between 1891 and 1896 German aeronautical engineer Otto Lilienthal made thousands of successful flights in hang gliders of his own design. American aviators Orville Wright and Wilbur Wright of Dayton, Ohio, are considered the fathers of the first successful piloted heavier-than-air flying machine. Through their scientific research and engineering, the Wright brothers put together the combination of critical characteristics that other designs of the day lacked -- a relatively lightweight powerful engine; a reliable transmission and efficient propellers; an effective system for controlling the aircraft; and a wing structure that was both strong and lightweight. At Kitty Hawk, North Carolina, on December 17, 1903, Orville Wright made the first successful flight of a piloted, heavier-than-air, self propelled craft, called the Flyer. That first flight traveled a distance of about 120 ft. The distance was less than the wingspan of many modern airliners, but it represented the beginning of a new age in technology and human achievement. Their fourth and final flight of the day lasted 59 seconds and covered only 852 ft. The third Flyer, which the Wrights constructed in 1905, was the world's first fully practical airplane. It could bank, turn, circle, make figure eights, and remain in the air for as long as the fuel lasted, up to half and hour on occasion.
             The airplane, like many other milestone inventions throughout history, was not immediately recognized for its potential. During the 1900s, prior to World
             War I (1914-1918), the airplane was relegated mostly to the county-fair circuit, where daredevil pilots drew large crowds but few investors. One exception was the United States War Department, which had long been using balloons to observe the battlefield and expressed an interest in heavier-than-air craft as early as...