High Quality Content by WIKIPEDIA articles! No. 666 Squadron RCAF was originally an RCAF Air Observation Post (AOP) squadron formed during the Second World War. It was manned principally by Royal Canadian Artillery (RCA) and Royal Canadian Air Force (RCAF) personnel. Numbers 651 to 663 Squadrons of the RAF were Air Observation Post units working closely with army units in artillery spotting and liaison. Three additional squadrons were Canadian, and approved on the RCAF list in the late summer of 1944: No. 664 Squadron RCAF, No. 665 Squadron RCAF, and No. 666 Squadron RCAF. The Canadian pilots were officers recruited from the Royal Canadian Artillery and trained to fly at 22 E.F.T.S. Cambridge, and further trained for operational flying at No. 43 Operational Training Unit RAF, at RAF Andover.