List of Royal Air Force conversion units

Conversion units and operational conversion units (OCU) were training units of the Royal Air Force.

History
With the introduction of new heavy bombers, the four-engined Short Stirling, Avro Lancaster and Handley Page Halifax, the Royal Air Force introduced heavy conversion units. The heavy conversion units began forming in late 1941, to qualify crews trained on medium bombers to operate the heavy bombers prior to an assignment to an operational training unit to gain experience before final posting to the operational squadrons.

After the end of the Second World War, their role was taken over by the operational conversion units. Although the units had nominal bases, it was usual for different flights and individual aircraft to be detached nearer the operational bases. Some of the heavy conversion units were involved in bombing operations over Germany.

Royal Air Force Operational Conversion Units (OCU) are training units that prepare aircrew for operations on a particular type or types of aircraft or roles. Some OCUs have a shadow, or reserve, squadron designation which is used if the unit has a war role.