The ADEN cannon is a British autocannon which has been mounted on many military aircraft. Designed in the 1940s, the ADEN entered service on the Hawker Hunter in 1954, and was the standard aerial gun of the Royal Air Force and Fleet Air Arm until the introduction of the Panavia Tornado in the 1980s. The ADEN also saw very wide international service, being used by over 30 different countries. It is comparable to the French DEFA cannon with which it can share ammunition.