An escadrille (literal translations: "squad" or "small squadron") is a type of military unit, most often found in the air forces of some French speaking countries. While the term is frequently translated into English as "squadron", an escadrille was originally a smaller unit (whereas the French escadron, in the context of aviation is a much larger unit, comparable in status to a naval squadron).
The first air escadrilles were formed in France before World War I, in 1912. They were initially a loosely defined group of aircraft capable of similar tasks, in most cases not more than six aeroplanes in each. During the war the escadrille became the basic independent unit of aviation within the French armed forces. An escadrille was a homogeneous unit, armed with a single type of aeroplane, with permanent flying and ground personnel attached, motorised transport and tent hangars. By mid-1915 the Armee de l'Air had grown to 119 escadrilles of 10 aircraft each: 14 of fighters, 50 of bombers and the rest reconnaissance, spotter and communications units. While escadrilles initially operated independently, during the Battle of Verdun (1916), chasseur (fighter) escadrilles were formed into larger formations, for easier coordination.
During World War II, French escadrilles usually fielded between 10 and 12 aircraft. Hence they were roughly equivalent to a German staffel, Italian gruppo or Polish eskadra (10 aircraft in 1939). This was in contrast to air squadrons of the British Commonwealth or United States, which usually had 12–18 aircraft, divided into two to four flights.
Until 1949, between one and four French escadrilles formed a groupe. Since then, however, escadrilles have been subordinate to escadrons. As such, groupes and escadrons are the equivalent of the German language terms gruppe and geschwader; and the English language terms "wing" and "group" (the definitions of which also vary from one nation to another).