The Avro Vulcan, sometimes referred to as the Hawker Siddeley Vulcan, is a delta wing subsonic jet strategic bomber that was operated by the Royal Air Force (RAF) from 1953 until 1984. It was developed in response to a specification released by the Air Ministry. At the time, both jet engines and delta wings were considered cutting-edge and relatively unexplored; thus, the small-scale Avro 707 was produced to test the principles of the design. In flight, the Vulcan was an agile aircraft for its size. The RAF began retiring these airframes in 1986, with the last one XH558 in 2016.