During the middle twenties the names of Wright, Curtiss, and Martin were still to the fore. The Wright Aëronautical Corporation was the leader in its field. Its liquid-cooled engines had grown from 120-horsepower to 300-, 400-, 675-horsepower. It also had begun to experiment with and develop an air-cooled radial airplane engine. This engine, invented by Charles L. Lawrance, was a result of his study of the Manley radial engine built for Professor Langley’s _Aerodrome_. The Manley engine was far ahead of its time. What might have happened had the first Wright plane and the Manley engine come together in the early days is pure guesswork. The original Manley radial engine weighed only 3.6 pounds per horsepower. In the early twenties, when Lawrance started to work with the Manley engine as a guide, airplane engines weighed about 10 pounds per horsepower. The Manley engine used in the _Aerodrome_ was water-cooled and Lawrance went to work to eliminate the extra weight caused by radiator and water-cooling equipment. So successful were his first experiments that he joined the Wright Aëronautical Corporation to collaborate in developing an aircraft engine that was to have a profound influence on world aviation. During this time the Curtiss Company continued to build successful airplanes for both the Army and the Navy, including the first of the famous Hawk fighters, completed in 1923. Martin worked on improved types of Army bombers and Douglas built planes for both branches of the service. In Seattle, Washington, the Boeing Company had started its first aircraft for the Army. New names such as Beech, Cessna, Sikorsky, Vought, Fairchild, Northrop, and others began to appear on the nameplates of new planes. In the early twenties, with transcontinental mail service well under way, there were many attempts made to establish air transport and cargo services. Most of these ventures were undertaken by former military aviators, using cast-off Army airplanes. Their airports usually were cow pastures. They planned their own air routes and got their weather reports from the newspapers. Bad weather would often ground a flight and passengers were almost as uncertain as the weather. Many of those pioneer operators had to depend on the dollar-a-ride hops of Sunday sightseers to “keep the wolf from the door.” One service operated 14-passenger converted Navy seaplanes on a route between New York and Havana, and another route between Cleveland and Detroit. Most of these pioneer air transport Operations lasted for only a short time, due to the heavy cost of maintaining the planes and the lack of properly marked air routes. [Illustration]