George Cayley (1773-1857) is considered the father of aviation. Cayley was a relatively well to do baronet who lived on an estate in Yorkshire, England. An educated man, Cayley spent his life working intensely on engineering, social, and political problems in England. However, the dominant interest of his life was heavier-than-air flight, and in 1799 he set forth for the first time in history the concept of the modern airplane.
Cayley had identified the drag vector (parallel to the flow) and the lift vector (perpendicular to the flow). It was this concept which was to be utilized by the Wright brothers in the first successful airplane more than a century later.
In 1804 Cayley built a whirling arm apparatus just as John Smeaton (1724-1792) had done earlier to study the resistance of air on cloth surfaces. At the end of this whirling arm was a lifting surface (a portion of a wing) on which Cayley measured force of lift. Also in 1804, he designed, built, and flew a small model glider. In 1804 this glider represented the first modern configuration airplane in history, with a fixed wing, and a horizontal and vertical tail that could be adjusted. He found that setting the wings at a slight dihedral gave lateral stability and that a tail plane set behind the main wings gave longitudal stability.3 In 1809 and 1810 Cayley published three papers on his aeronautical research where he quite correctly pointed out for the first time that: (1) lift is generated by a region of low pressure on the upper surface of the wing and; (2) cambered wings (curved surfaces) generate lift more efficiently than a flat surface. These results, among many others, can be found in his papers entitled "On Aerial Navigation" published in the November 1809, February 1810, and March 1810 issues of Nicholson's Journal of Natural Philosophy.4 This "triple paper" by Cayley ranks as one of the most important aeronautical documents in history.5 In 1849, he designed, built, and tested a full-size triplane glider, which during some of its tests carried a ten-year-old boy through the air several yards on a descending hill. For this reason, the machine is sometimes called "Cayley's boy carrier." One of Cayley's other designs appeared in Mechanics Magazine in 1852.6 Cayley never achieved his final goal--sustained heavier-than air, powered, manned flight. However, his contributions clearly furthered advancement to the modern airplane.
At 10:30 A.M. on December 17, 1903, Orville Wright achieved the first piloted, sustained, controlled and powered flight. His brother, Wilbur Wright, stood by and timed the flight with a stopwatch. The first flight lasted twelve seconds and the aircraft flew 100 yards. The location was Kill Devil Hills, near Kitty Hawk in North Carolina. After four years of experiments with kites, gliders and wind tunnel testing, the Wright Brothers finally achieved their dream. Three more flights were made that day and the longest was nearly a minute and covered more than half a mile. They designed their own engine with the aid of their bicycle mechanic, Charlie Taylor. He designed and built an original engine that just met the Wright Brothers minimum specifications. The propellers were remarkably efficient considering there was almost complete lack of knowledge on this subject at this time. Wilbur Wright was the first person to recognize that a propeller is nothing more than a twisted wing, where the "lift" force is now pointing forward for propulsion. Using his theory in conjunction with their airfoil data measured during previous wind tunnel testing, Wilbur designed and constructed a remarkably efficient propeller. This aspect of the Wright brothers' technology is sometimes not fully appreciated, yet it was one of the most important technical victories that led to their success. Wing warping was used for lateral control. Wilbur conceived the idea of bending, or deflecting, the tips of wings to achieve lateral control around the longitudinal axis of an aircraft. The concept of wing warping was another one of the major ingredients for the Wright's success. The Wright Brothers were the first to treat a flying machine as an integrated system involving aerodynamics, propulsion, structures, and flight dynamics. They fully appreciated the interaction and mutual importance of all these aspects. In this sense, they were the first to build a total flying machine, which encompassed all of the major aspects of a modern airplane.
According to the aviation historian Roger Bilstein, it is uncertain when the first scheduled passenger service in the United States began. Silas Christofferson carried passengers in 1913 by hydroplane between San Francisco and Oakland harbors. In 1914, the St. Petersburg-Tampa Airboat line carried passengers between Tampa and St. Petersburg, Florida, using a Benoist flying boat. The service was quite successful.
After the war ended, Alfred W. Lawson built the first multiengine airplane designed exclusively for passengers—the Lawson C-2 in 1919. But surplus military aircraft were a lot cheaper to buy than the C-2, and his plane did not sell. Next, Lawson built a “jumbo” airliner, the L-4, that carried 34 passengers and 6,000 pounds (2,722 kilograms) of mail. This giant plane, however, crashed on its first test flight, ending further development.
In 1920, a Florida entrepreneur, Inglis Uppercu, began to offer international passenger flights from Key West, Florida, to Havana, Cuba. He later added other routes including flights between Miami and the Bahamas and soon between New York and Havana, picking up passengers at stops along the way. He even extended his service to the Midwest, flying between Cleveland, Ohio, and Detroit, Michigan. His Aeromarine Airways' 15 flying boats, dubbed “airborne limousines,” made more than 2,000 scheduled flights and carried nearly 10,000 passengers. But one of their planes crashed off the coast of Florida, four passengers drowned, and Aeromarine Airways went out of business in 1924.
It was the Post Office and airmail delivery that gave the commercial airlines their true start. In the early part of the 20th century, the Post Office had used mostly railroads to transport mail between cities. By 1925, only seven years after the first official airmail flight, U.S. Post Office airplanes were delivering 14 million letters and packages a year and were maintaining regular flight schedules. Airmail appealed particularly to bankers and other businessmen who regularly began to use it to move checks and financial documents more quickly, reducing the “float” on checks and the length of time that funds were idle and unavailable for use.
Once airmail became accepted, the government transferred airmail service to private companies. Representative Clyde Kelly of Pennsylvania sponsored the Contract Air Mail Act of 1925, commonly referred to as the Kelly Act. This was the first major step toward the creation of a private and profitable U.S. airline industry.
After the Kelly Act passed, private companies bid on feeder routes that supplemented the transcontinental air route. This airway had expanded during the nine years that the Post Office had transported mail by air. Now the Post Office awarded contracts to private companies, and these companies would later become transportation giants.