2014, Lockheed Martin announced that they would offer refurbished and remanufactured S-3s, dubbed the C-3, as a replacement for the Northrop Grumman C-2A Greyhound for carrier onboard delivery. The requirement for 35 aircraft would be met from the 91 S-3s currently in storage. In February 2015, the Navy announced that the Bell Boeing V-22 Osprey had been selected to replace the C-2 for the COD mission. Variants S-3A First production version, 187 built. S-3B Upgraded avionics, AN/APS-137 inverse synthetic aperture radar, Joint Tactical Information Distribution System, AGM-84 Harpoon launch capability, first flight 13 September 1984, 119 converted from S-3As. ES-3A Shadow Designed as a carrier-based, subsonic, all-weather, long-range, electronic reconnaissance (ELINT) aircraft. 16 aircraft were modified to replace the EA-3B Skywarrior, entering fleet service in 1993. The ES-3A carried an extensive suite of electronic sensors and communications gear, replacing the S-3's submarine detection, armament, and maritime surveillance equipment with avionics racks accommodating the ES-3A's sensors. These modifications had minor impact on airspeed, reducing its top rated speed from but had no noticeable impact on the aircraft's range and actually increased its rated loiter time. Because these aircraft were standoff indications and warnings platforms and were never intended to be part of an ingress strike package, yet this new speed limitation was considered insignificant. KS-3A Proposed dedicated air tanker with fuel capacity of 4,382 US gal (16,600 L), one converted from YS-3A, later converted to US-3A. KS-3B Proposed air tanker based on S-3B and utilizing the buddy refueling system, not built. US-3A S-3A modified for carrier onboard delivery, capacity for six passengers or 4,680 lb (2,120 kg) of cargo, retired in 1998. Aladdin Viking Conversion of six aircraft for overland surveillance and Elint missions. May have dropped ground sensors in the Bosnian War. Beartrap Viking S-3Bs fitted with still-classified modifications. Calypso Viking Proposed anti-smuggling variant, not built. Gray Wolf Viking One aircraft fitted with AN/APG-76 radar in a modified cargo pod under the wing. Also dubbed SeaSTARS in reference to E-8 Joint STARS. Orca Viking Avionics testbed. Outlaw Viking One S-3B fitted with Over-the-horizon Airborne Sensor Information System (OASIS III), returned to regular S-3B in 1998. This particular Viking is now on display at the USS Midway Museum, located on the decommissioned . NASA Viking One aircraft was extensively rebuilt into a state-of-the-art NASA research aircraft. The Navy's Fleet Readiness Center Southeast and a Boeing facility in Florida modified it, adding