What type of aircraft was primarily used for observation at the beginning of World War I?

The type of aircraft primarily used for observation at the beginning of World War I was airplanes. During the early stages of the war, military forces quickly recognized the strategic importance of aerial reconnaissance. Airplanes were initially adapted from civilian aircraft and designed for the primary role of scouting enemy positions, gathering intelligence, and relaying information back to commands. They were crucial in obtaining a clearer picture of the battlefield and identifying troop movements, which was essential for planning military operations.

Fighter aircraft, while developed later to engage in aerial combat and protect reconnaissance missions, were not the primary aircraft used for observation at the war's onset. Bombers came into play as strategies evolved, focusing on carrying out attacks against ground targets rather than reconnaissance. Trainers were designed specifically to help teach aviators how to fly and were not utilized in combat roles or for observation purposes. Thus, airplanes, in their early reconnaissance form, served as the backbone of aviation surveillance during the first years of the conflict.