The beginning of World War I, in Europe, saw the first use of the airplane by the military. At first, warring pilots flying over the battle lines actually exchanged friendly waves in passing. This was the expression of brotherly feeling among men who already had risked their lives to conquer the flying machine. But this knightly feeling did not last long. One belligerent flier carried a rifle aloft. This rifle inspired the thought of the machine gun, and war in the air, as in the trenches, became a survival of the fittest. In the United States, the Aviation Section, Signal Corps, U. S. Army, was just two weeks old. When it was created on July 18, 1914, the Aviation Section had an authorized personnel of 60 officers and 260 enlisted men, and a few airplanes. In Europe, every major power boasted of hundreds of planes. The year 1916, two years after the start of World War I, saw Army aviation in its first offensive action. Eight low-powered planes engaged in a punitive expedition against Mexican bandits. The chief result of this expedition was the severe newspaper criticism of the poor showing made by our fliers and America’s lack of improved types of combat planes. As the result of the criticism created by the Mexican expedition, Congress, in June, 1916, voted funds for the expansion of Army aviation. But aviation development required time and, actually, when the United States went into World War I on April 6, 1917, Army aviation consisted of but 65 officers (including only 35 fliers), 1,087 enlisted men, and 55 airplanes. All of the planes were obsolete and none carried machine guns. Thus, with no military planes suitable for use against a well-equipped enemy, no fliers trained in the use of high-powered fighting planes and aërial machine guns, and with few factories that had had any previous experience in the production of airplanes, America plunged into the midst of World War I. Although a little late, America went to work. Having no good combat designs of our own, our fliers fought in British and French airplanes. We developed the best training plane in the world, the Curtiss JN-_Jenny_ (page 32), and trained 15,000 flying cadets. By March, 1918, our Army Aviation strength was 11,000 officers and 120,000 enlisted men. At the time of the Armistice we had 757 pilots, 481 observers, with 740 planes at the front and 1,402 pilots and 769 airplanes in the Zone of Advance, ready for combat. Our pilots were credited with the destruction of 491 enemy airplanes, of which 462 were accounted for by 63 airmen. We had produced 26 aces, each of whom had destroyed five or more enemy aircraft. [Illustration: FIGHTING PLANES OF WORLD WAR I BRITISH DH-4 BRITISH _CAMEL_ GERMAN _ALBATROS_ GERMAN FOKKER FRENCH _SPAD_] [Illustration] THE FIRST TRANSATLANTIC FLIGHT