One of the most important breakthroughs in military technology associated with World War I, and certainly the one that continues to capture the public imagination, was the use of airplanes, which were a virtual novelty a decade before. While the war quickly ground to a halt in its first few months, the skies above the Western Front became increasingly busy. The great powers had already been acquiring aircraft for potential uses, but given that aerial warfare had never been a major component of any conflict, it's understandable that few on either side had any idea what the planes were capable of doing. Furthermore, at the start of the war, all sides' aircraft were ill-equipped for combat mostly because the idea that planes might somehow fight was still a novel one, and the adaptations had not yet been developed that would allow the aerial battles later in the war.

As a result, aircraft were used almost entirely for reconnaissance early on, allowing generals to gain unprecedented levels of information about enemy movements. Such intelligence allowed the French to counter German movements in what became the First Battle of the Marne, ending Germany's hopes for victory through the Schlieffen plan. Similarly, in the east, German planes were vital in tracking, encircling and destroying Russian forces at Tannenberg.

The Royal Air Force (RAF), Britain's legendary air arm, was born in the skies above the First World War. The British had previously used balloons for spotting and reconnaissance for decades, and in the years leading up to the war, planes started seeing military use. They mostly provided reconnaissance, though experiments were made in using them offensively. During the Boer War of 1899-1902, the British Army used the crews of helium-filled balloons to plot and help target artillery fire. But these were small, tentative steps. The first patent to fit a machine gun to a plane, taken out in 1910, had not yet led to active fighting vehicles.