Which body was responsible for aviation before the establishment of the US Army Air Service?

The primary responsibility for aviation within the U.S. military before the establishment of the Army Air Service in 1918 rested with the Signal Corps. The Signal Corps was tasked with the development and operation of military aviation and was crucial in the early formation of aerial capabilities during World War I. They oversaw the initial experiments with balloons and reconnaissance flights and were responsible for training pilots and managing aviation resources. This laid the groundwork for the eventual establishment of a dedicated air service that would focus exclusively on aerial combat and support.

In contrast, the U.S. Navy had its own aviation developments, but its efforts were separate from the responsibilities of the Army. The Department of Defense did not exist during this period; it was created in 1947, long after aviation responsibilities were assigned within the military. The U.S. Coast Guard, while operating its own aviation units, was also not responsible for military aviation in the context of the Army or the broader Air Service mission. Thus, the Signal Corps is recognized as the pivotal body overseeing aviation at the time, making it the correct choice.