During the First World War, many of the Coventry motor car firms turned to aeroplanes and engines, but the industry did not assume importance until 1920, when Sir WG Armstrong-Whitworth's Aircraft Company was formed by a merger of the Newcastle firm with Siddeley Deasey of Coventry. In 1923 they moved from London Road to Whitley, where the Siskin trainer and fighter planes were made, followed by civil aircraft from 1926 onwards.

The Armstrong Siddeley Development Company which controlled Armstrong Whitworth, became part of the Hawker Siddeley Aircraft Company in 1935 and a new factory at Baginton was opened the following year, to produce the famous Whitley plane. Alvis entered the field of aeroengine manufacture at this time and were still in production in 1963.

The Second World War saw the chief motor works once more producing armaments, and Daimler, Rover, Austin and Rootes worked together to manufacture aeroengines with Armstrong Whitworth engaged on the production of Lancasters and Stirlings. The company entered the jet age with contracts for Meteors in 1949, and by the mid-1950's had designed the Argosy, a successful freight-carrying aircraft built to military specifications.