The Britten-Norman Islander, and later the Defender (an upgraded version of the aircraft) was introduced into service as a replacement for the ageing Beaver. It is one of two types of fixed-wing aircraft operated by the Army Air Corps, the other being the Firefly of the DEFTS. It is usually employed in a surveillance capacity, however it also has a limited use in transporting personnel.

This aircraft has been extensively used in Northern Ireland. Other roles include air photography, airborne command post and liaison flying. Notably it contains a full Instrument Flying Procedural and Navigation fit.