on the mission computer, which would often "dump" during the stress of a catapult-assisted take-off, requiring the crew to restart it and reload the software. The U.S. Navy had also purchased an insufficient number of spare parts, which negatively impacted the aircraft's mission readiness. Performance improved considerably once an ample supply of spares was provisioned, allowing the S-3 to become a valuable ASW asset as well as a good surface-surveillance platform as well. Starting in 1987, the majority of S-3As were progressively upgraded to the improved S-3B standard; the involved the addition of several new sensors, avionics, and weapons systems, which included the capability to launch the AGM-84 Harpoon anti-ship missile. The S-3B could also be fitted with "buddy stores", external fuel tanks that allowed the Viking to refuel other aircraft. During July 1988, VS-30 became the first fleet squadron to receive the enhanced capability Harpoon/ISAR equipped S-3B, based at NAS Cecil Field in Jacksonville, Florida. Additional, often more specialised variants, were also produced. 16 S-3As were converted to ES-3A Shadows for carrier-based electronic intelligence (ELINT) duties. Six aircraft, designated US-3A, were converted for a specialized utility and limited cargo Carrier onboard delivery (COD) requirement. This model played a key role in US military efforts to relieve the Iran hostage crisis of 1979-1981. Plans were also made to develop the KS-3A carrier-based tanker aircraft, but this program was ultimately cancelled after the conversion of just one early development S-3A. As a consequence of the collapse of the Soviet Union and the breakup of the Warsaw Pact in the early 1990s, the Soviet-Russian submarine threat was perceived as much reduced, and the Vikings had the majority of their antisubmarine warfare equipment removed. The aircraft's mission subsequently changed to sea surface search, sea and ground attack, over-the-horizon targeting, and aircraft refueling. As a result, the S-3B after 1997 was typically crewed by a single pilot along with a copilot [NFO]; the additional seats remained in place in the S-3B and could be used by additional crew members for certain missions. To reflect these new missions, the Viking squadrons were redesignated from "Air Antisubmarine Warfare Squadrons" to "Sea Control Squadrons". Prior to the aircraft's retirement from front-line fleet use aboard US aircraft carriers, a number of upgrade programs were implemented. These include the Carrier Airborne Inertial Navigation System II (CAINS II) upgrade, which replaced older inertial navigation hardware with ring laser gyroscopes with