The film depicts the role of air defence over Canada and the United States by following the training and operational exercises of a RCAF squadron.

On a deployment to CFB Cold Lake, Alberta, where training for RCAF operational units takes place, experienced flight crews and newcomers in the squadron learn how to be more effective as a team.

Air defence was based on radar stations, staffed with American and Canadian personnel, set up in three systems across Canada to detect incoming Soviet bombers.

[Note 1] Typical of the NFB's series of short training films for the RCAF, Canada's Air Defence relied heavily on military assistance in obtaining footage.

Canada's Air Defence was primarily a military training film, produced as part of the NFB's newsreel programs.