During the 1930s, a major expansion of the Royal Air Force (RAF) had been directed by the British government, which led to the formulation and issuing of a number of operational requirements by the Air Ministry. One of these was Operational Requirement 42 (OR.42), which sought an advanced training aircraft to be specifically used by aircrews destined to serve on bomber aircraft. As the RAF was in the process of migrating from biplanes to monoplanes, which were capable of greater speeds and had more demanding flight characteristics, a suitable trainer was needed to match this step change. At one point, the Avro Anson was considered for the role, however, it was thought that an aircraft more difficult to fly would be necessary. Accordingly, on 10 July 1936, Specification T.23/36 was issued to Airspeed for the development of a twin-engined training aircraft to meet OR.42.