No. 664 Squadron was a Royal Air Force Air Observation Post squadron associated with the Canadian 1st Army and later part of the Royal Auxiliary Air Force. 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, 664–666, were manned with Canadian personnel. Their duties and squadron numbers were transferred to the Army with the formation of the Army Air Corps on 1 September 1957.