The S-3B Viking carries out the US Navy's carrier-based sea control mission. The S-3 was originally designed in the early 1970s with a sophisticated anti-submarine warfare sensor suite. The demise of the Soviet Union and the increasing dominance of littoral warfare led to decreased emphasis on the anti-submarine warfare and more emphasis on anti-surface warfare and land-attack missions.
The S-3A variant was replaced in the early 1990s by the S-3B. This incorporates upgrades such as the APS-137 inverse synthetic aperture radar and the AGM-84 anti-ship missiles. Each carrier air wing includes one sea control (VS) squadron equipped with eight S-3Bs. VS squadrons perform anti-submarine, anti-shipping, mine-laying, and surveillance missions for the carrier group.
Sixteen S-3A were converted to ES-3A Shadow standard during the early 1990s with a variety of electronic surveillance and intercept equipment to locate ant identify hostile emitters and communications stations. In mid-1998, the Navy made the decision to with draw the ES-3A from service without replacement. The aircraft's mission avionics suite, becoming obsolescent in the age of interconnectivity in the electronic battlefield, was deemed as too expensive to upgrade - the ES-3A left service in mid-1999.
The S-3B has an important secondary role as an aerial tanker, equipped with D-704 buddy-buddy refuelling stores. As the sole carrier aircraft currently capable of this function, the number of S-3Bs per squadron has been increased from six to eight. Several upgrades are being installed on Vikings, including the GPS, carrier aircraft inertial navigation system II, new tactical displays, computer memory, satellite-communication equipment and improved radios. Several S-3Bs have been involved in anti-drug trafficking duties, using camera systems, forward-looking infra red and hand-held sensors. The S-3B is planned for replacement from 2015 by a variant of the Common Support Aircraft.