Observation balloon in the context of "Royal Flying Corps"

World War I was the first major conflict involving the use of aircraft. Tethered observation balloons had already been employed in several wars and would be used extensively for artillery spotting. Germany employed Zeppelins for reconnaissance over the North Sea and Baltic and also for strategic bombing raids over Britain and the Eastern Front.

Airplanes were just coming into military use at the outset of the war. Initially, they were used mostly for reconnaissance. Pilots and engineers learned from experience, leading to the development of many specialized types, including fighters, bombers, and trench strafers.

The Imperial Japanese Army Air Service (IJAAS) or Imperial Japanese Army Air Force (IJAAF; Japanese: 大日本帝國陸軍航空部隊, romanized: Dainippon Teikoku Rikugun Kōkūbutai, lit. 'Greater Japan Empire Army Air Corps') was the aviation force of the Imperial Japanese Army (IJA). Its primary mission was to provide tactical close air support for ground forces, as well as a limited air interdiction capability. The IJAAS also provided aerial reconnaissance to other branches of the IJA. While the IJAAS engaged in strategic bombing of cities such as Shanghai, Nanjing, Canton, Chongqing, Rangoon, and Mandalay, this was not the primary mission of the IJAAS, and it lacked a heavy bomber force.

It did not usually control artillery spotter/observer aircraft; artillery battalions controlled the light aircraft and balloons that operated in these roles.

The Deutsche Luftstreitkräfte (German: [ˈdɔʏtʃə ˈlʊftˌʃtʁaɪtkʁɛftə], German Air Combat Forces) – known before October 1916 as Die Fliegertruppen des deutschen Kaiserreiches (The Imperial German Air Service, lit. "The flying troops of the German Imperial Realm") – was the air arm of the Imperial German Army. In English-language sources it is usually referred to as the Imperial German Air Service, although that is not a literal translation of either name. German naval aviators of the Marine-Fliegerabteilung were an integral part of the Imperial German Navy (Kaiserliche Marine). Both military branches operated aeroplanes, observation balloons and airships.