The Supermarine Channel (originally the Supermarine Channel Type) was a modified version of the AD Flying Boat, purchased by Supermarine from the British Air Ministry and modified for the civil market with the intention of beginning regular air flights across the English Channel. The aircraft were given airworthiness certificates in July 1919. The Mark I version, later called the Channel I, was powered with a 160 horsepower (120 kW) Beardmore engine; a variant designated as Channel II was fitted with a 240 horsepower (180 kW) Armstrong Siddeley Puma engine. Designed by Supermarine to accommodate up to four passengers, the company produced a series of interchangeable interiors that could be used at short notice, which enabled the Channel to be used as a fighter or for training purposes.