No. 665 "Air Observation Post" Squadron, RCAF was formed in England during the Second World War. It was manned principally by Royal Canadian Artillery (RCA) and Royal Canadian Air Force (RCAF) personnel, with select British artillery pilots briefly seconded to assist in squadron formation. Numbers 651 to 663 Squadrons of the RAF were Air Observation Post units working closely with Army units in artillery spotting and liaison. A further three of these squadrons – Nos. 664, 665 and 666 – were RCAF AOP squadrons manned by Canadian and British personnel.