The Avro Type 694, better known as the Avro Lincoln, was a British four-engined heavy bomber, which first flew on 9 June 1944. Developed from the Avro Lancaster, the first Lincoln variants were known initially as the Lancaster IV and V, but were renamed Lincoln I and II. It was the last piston-engined bomber used by the Royal Air Force. In all, 604 Lincolns were built. The type also saw significant service with the Royal Australian Air Force (RAAF) and Fuerza Aérea Argentina (Argentine Air Force), as well as some civil aviation usage.