The Bell AH-1 Cobra is an attack helicopter. It shares a common engine, transmission and rotor system with the older UH-1 "Huey". It is variously called the "Huey Cobra," "Sea Cobra," "Super Cobra," "Whiskey Cobra," "Zulu Cobra," "Viper," or "Snake"; depending on the model. Once the backbone of the United States Army attack helicopter fleet, the AH-1 has been fully replaced by the AH-64 Apache in US Army service. Upgraded versions continue to fly with the United States Marine Corps, the Islamic Republic of Iran Army Aviation and Islamic Revolutionary Guards Corps Air Force, the Israeli Air Force, the Japan Self Defense Forces, the Republic of China Army, the Pakistan Army, the Republic of Korea Army and several other users.