The Douglas A-3 Skywarrior was a strategic bomber built for the United States Navy and among the longest serving carrier-based jet aircraft. It entered service in the mid-1950s and was retired in 1991. For many years after its introduction, it was also the heaviest aircraft ever flown from an aircraft carrier, earning it the unofficial nickname "The Whale".[1][2] Its primary function for much of its later service life was as an electronic warfare platform, tactical air reconnaissance platform, and high capacity aerial refueling tanker. A modified derivative also served in the U.S. Air Force until the early 1970s as the B-66 Destroyer. The Skywarrior is one of only two Navy attack aircraft intended as a strategic bomber to enter service. The Martin P6M SeaMaster tested well, but never entered service due to the Navy fearing loss of funding for surface ships and submarines if it encroached on the USAF strategic bomber role. The pending elimination of the flying-boat platform from the United States Navy also entered into the decision regarding the P6M. Later the carrier-based supersonic A-5 Vigilante was also originally designed for strategic nuclear strike missions. However, with the removal of aircraft carriers from the Single Integrated Operational Plan (SIOP) and the transfer of the Navy's strategic nuclear deterrence mission to the Fleet Ballistic Missile (FBM) submarine force, the Vigilante also saw its mission changed, in its case to carrier-based tactical air reconnaissance.