The Avro 504 is a single-engine biplane bomber made by the Avro aircraft company and under license by others. Production began during World War I—with 8,970 built during the conflict—and continued globally for almost 20 years,[2] making it the most-produced aircraft of any kind that served in any military capacity during the First World War. More than 10,000 were built from 1913 until production ended in 1932