There have been five carriers in the history of the RCN. HMS Bonaventure was purpose-built for Canada while others were leased from the UK (or manned by Canadians).
HMCS BONAVENTURE was Canada’s last aircraft carrier. The scrapping of this ship in the early ’70’s had such a traumatic effect on the Royal Canadian Navy (RCN) that when I joined in the mid-80’s those few sailors that remained who had served on her were treated with special reverence and held in high esteem. Even today, there is a common joke among younger sailors that their bosses are so experienced that “they served on the Bonnie”.
Canada first ventured into seaborne naval aviation in WWII when the RN, facing a manpower crisis, asked if the RCN could man two escort carriers (HM ships PUNCHER and NABOB). The ship’s companies were Canadians, the air department was RN.
With this experience and facing a potential showdown with the USSR and its’ allies post-WWII, the Canadian government decided that the RCN should have two aircraft carriers. This was later reduced to a requirement for one carrier, mostly for financial reasons.
To develop the capability, the RN ‘loaned’ the RCN the carrier WARRIOR. For a few years, the RCN trained with this ship and learned much about running a fleet carrier.
Through the 50’s the RCN ‘leased’ the carrier MAGNIFICENT from the RN and put it into operation. During its’ life in the RCN, the Canadians defined their own carrier-based doctrine and requirements.
The MAGNIFICENT was returned to the RN when a Majestic class carrier started in 1943 but not completed at wars end, was finished to Canadian specifications. This ship became HMCS BONAVENTURE.
The ship served until 1970 when for a number of political, fiscal and doctrinal reasons, the ship was decommissioned and scrapped. While this was not the end of Canadian naval aviation at sea, it was the end of Canadian carrier capability.
References:
https://forums.armchairgeneral.com/forum/historical-events-eras/weapons-of-war/naval-warfare/130719-the-rise-and-fall-of-canadian-carrier-aviation
http://www.shearwateraviationmuseum.ns.ca/ships/ameer.htm