At the outbreak of World War I in July of 1914, airplanes (or known then as "aeroplanes") were still in their infancy. Invented barely 10 years previously, they were made by hand from cloth, wire, and wood. The engines fitted to them were less powerful and less reliable than those in modern automobiles. They were painfully slow and all too prone to accidents. Yet it didn't take long for military commanders to find potential applications and discover the effectiveness of these radical new machines.
Manned balloons and dirigibles had been around since the 18th and 19th centuries, respectively, making manned flight almost a common occurrence by 1900. Just by the virtue of being high above the ground, any flying (or floating) machine was automatically useful for observation, photography, and cartography. Later, even the primitive biplanes of the 1910s were faster than dirigibles, giving them a unique capability of moving from point A to point B. This gave the user the crucial advantage of being able to snoop around behind enemy lines, locating strongholds and weak spots.
Even before World War I, airplanes had seen limited front-line use. France, Italy, the United States, Turkey, Bulgaria, Greece, Serbia, Romania, and Mexico had all used military aircraft from 1911-1913 for short-range observation and long-range reconnaissance missions. Later, these roles were expanded to include bombing ground targets. History's first bombing attacks caused few, if any casualties, but the psychological effect of being raided from the air was (and still is) terrifying to no end. Airplanes gradually started to carry more sizeable bomb loads, and strategic bombing had become a reality by the end of the decade.
With the outbreak of World War I, and with observation and bomber aircraft becoming increasingly common, the belligerents inevitably started looking for a way to gain "air superiority," or control of the airspace around their positions. To begin with, pilots on opposing sides were fairly civilized towards one another, even exchanging friendly smiles and waves, although obscene gestures and armed combat were quick to follow. Early air-to-air weapons were crude, sometimes consisting of bricks, grappling hooks, and even the airplane itself, though a ramming assault would normally be suicidal for the attacking pilot. Like the cavalrymen they were destined to replace, airmen would soon be issued pistols and carbines.
Although somewhat effective, pistols did not have the required range or power to bring down an airplane, and box-magazine-fed bolt-action carbines were unlikely to hit a moving target. Both the Allies and Central Powers (primarily Germany and Austria-Hungary) attempted to mount machine guns on airplanes, recognizing the advantages of the "spray and pray" approach to accuracy. The guns were nearly always fixed to fire directly ahead in order to reduce pilot workload. This only required him to point the airplane in order to aim the guns, allowing him to maintain line-of-sight accuracy. Early attempts to fire through the propeller arc ended in disaster, with numerous pilots destroying their own propeller and effectively shooting themselves down. Such weapons would remain impractical in the air until the German Fokker E.III introduced a successful synchronization system.
Until the Allies figured out the synchronization problem, a workable, if imperfect, solution was to mount the machine gun on the top wing. This allowed the bullets to fire over the propeller, and special mounts were eventually devised to bring the breech backward and downward, closer to the pilot for easy reloading and unjamming. More importantly, these devices allowed the pilot to shoot upwards, which proved to be an excellent way of sneaking up on an unsuspecting reconnaissance or bomber pilot and attacking from his ventral blind spot. However, this mechanism did have some considerable flaws, most notably the vibration on the fragile structure of the top wing, resulting in poor accuracy and even catastrophic wing failure. These problems were rectified by the independent development of a reliable timing system, although the upward-firing mounts were still frequently included along with synchronized guns on late-war fighters like the Sopwith Dolphin.
Though it was commonly fighter pilots who became aces, it was not unheard of for an observer or bomber gunner to claim the title, and aviators flying in other roles were no less brave, skilled, or vital to the war effort. Though they never scored as many air-to-air victories as front line fighter pilots did, airmen in ground attack, heavy bomber, battlefield observation, maritime patrol, long-range reconnaissance, anti-submarine, trainer, utility, and experimental aircraft all filled a special niche in the combatant's war machines that would be impossible to fulfill in types designed for a different purpose.
Though flying was seen by many to be the escape from the slaughter on the ground, air combat was often just as stalemated as in the trenches below and perhaps even more dangerous than to the pilots of today. Anti-aircraft artillery and machine guns became ever more accurate; bombers packed their own defensive armament; interceptors were ready to defend ground targets at a moment's notice; and escort fighters swarmed around otherwise vulnerable observation balloons and dirigibles. Pilots were almost never equipped with parachutes, both to save precious weight and discourage cowardice. Instead, aviators were sometimes given a pistol as the "coward's way out" of a burning aircraft. Indeed, a number of pilots would end up perishing by their own hand instead of suffering an unimaginably awful flame-filled death. As a result of this inherent peril, high-scoring fighter pilots would earn fame from their countrymen and infamy from their enemies, and were often the subject of extensive propaganda campaigns on the home front.