In November 1936, in response to suggestions that the addition of flaps would aid in landing, a single Rapide was modified in order to explore their functionality. Based on this performance, in February 1937, de Havilland announced that flaps would be fitted to all production aircraft from that year onwards, while other improvements such as a downwards-facing recognition light and metal propellers could be fitted as options. From 1937, to signify the fitting of improved trailing edge flaps, aircraft thus equipped were accordingly re-designated as "DH.89A"; earlier-built Rapides were commonly retrofitted to this standard during their service life as well.