The Stirling was designed during the late 1930s by Short Brothers to conform with the requirements laid out in Air Ministry Specification B.12/36. Prior to this, the RAF had been primarily interested in developing increasingly capable twin-engined bombers but had been persuaded to investigate a prospective four-engined bomber as a result of promising foreign developments in the field. Out of the submissions made to the specification Supermarine proposed the Type 317, which was viewed as the favourite, whereas Short's submission, named the "S.29", was selected as an alternative. When the preferred Type 317 had to be abandoned the S.29, which later received the name "Stirling", proceeded to production.