Sikorsky Ilya Muromets

The Ilya Muromets is a Russian four-engine biplane built by the aircraft designer Igor Sikorsky, first flown in 1913 as the world's first four-engine aircraft and one of the first aircraft purpose-built to carry passengers in an enclosed cabin, with amenities including a heated interior and electric lighting. Built originally as a civil airliner before the outbreak of the First World War, the Ilya Muromets was converted for military use by the Imperial Russian Air Service as one of the world's first purpose-built heavy bombers, organized into a dedicated bomber squadron that carried out long-range raids while suffering remarkably few losses to enemy action relative to its extensive combat use. Its combination of size, range and multi-engine reliability influenced later heavy bomber and airliner design well beyond Russia.