These two engines were, however, of unquestioned value for advanced training purposes, the Hispano-Suiza in particular playing an important part in this work. Later another European engine, the 80 horse-power Rhone, was also put into production. * * * * * One of the serious mistakes into which the Allies had fallen at the time the United States entered the war was the development of such a multiplicity of types of engines and planes that it was impossible to have a large number of any one of them. Indeed, by the spring of 1917, there were almost as many types of planes skimming over the Western Front as there were types of motor-cars skimming over American roads. As a direct consequence of this condition, the trained personnel had grown to such proportions that it was estimated that from thirty to fifty men were required on the ground to keep each plane in the air. It was obvious, therefore, that unless this large number of trained attendants could be materially reduced, it would be hopeless to expect to put thousands of fighting planes into the air within a reasonable time, for, on this basis, 1,000 planes would require from 30,000 to 50,000 men to take care of them. It was realized, moreover, that copies of foreign designs could not be made available in time to answer the insistent demand that America should put on the front an air force of overwhelming proportions. Although, immediately upon the declaration of war, an aircraft commission had been sent to Europe for the purpose of gathering first-hand information, public sentiment would not have permitted the government to sit idly by and wait with folded hands for this commission to make its report. What the country demanded was action with a capital A. Now it is not generally known, perhaps, that, instead of engines being designed for certain types of aircraft, the most successful airplanes are designed around specific engines. And, as the development of the engine requires the greatest expenditure of effort and time, some one suggested that, instead of waiting for the members of the commission to come home and tell about the European engines they had seen, to manufacture which under American conditions might well prove impracticable, an all-American engine, combining the best features of the various European types but particularly adapted for manufacture under domestic conditions, be designed by the best engineering talent in the country and immediately placed in production. At a meeting of representatives of the Signal Corps—which then had charge of military aeronautics—and the Aircraft Production Board it was decided to put this suggestion into immediate execution, at the same time purchasing in Europe whatever equipment might be available in order to tide over the period while the all-American engine was being put into production.