Small numbers of early aircraft were purchased both by the Royal Flying Corps (RFC) and the Royal Naval Air Service (RNAS) prior to the start of World War I, and were taken to France when the war started. One of the RFC aircraft was the first British aircraft to be shot down by the Germans, on 22 August 1914. The pilot was 2nd Lt. Vincent Waterfall and his navigator Lt Charles George Gordon Bayly (both of 5 Sqn RFC). The RNAS used four 504s to form a special flight in order to bomb the Zeppelin works at Friedrichshafen on the shores of Lake Constance. Three set out from Belfort in north-eastern France on 21 November 1914, carrying four 20 lb (9 kg) bombs each. While one aircraft was shot down, the raid was successful, with several direct hits on the airship sheds and destroying the hydrogen plant.
Soon obsolete as a front-line aircraft, it came into its own as a trainer, with thousands being built in the war, with major production types being the 504J and the mass production 504K, which was designed with modified engine bearers to accommodate a range of engines, in order to cope with engine shortages. 8,340 Avro 504s had been produced by the end of 1918.