Editing Saab 37 Viggen (section)

=== Further development ===
[[File:Saab SF 37 Viggen 37951 F 13 Bråvalla 001.jpg|thumb|An SF 37 Viggen in flight, 1977]]
As the initial AJ 37 Viggen was being introduced to service, further variants of the Viggen proceeded to complete development and enter production.<ref name = "wagner 125">Wagner 2009, p. 125.</ref> In 1972, the first SK 37, an operational trainer variant with a staggered second canopy for an instructor, was delivered to the Swedish Air Force.<ref name = "fred 279" /><ref name="ford 616">Ford 1973. p. 616.</ref> On 21 May 1973, the first prototype of SF 37 Viggen, a tactical reconnaissance variant featuring a modified nose to accommodate seven sensors, conducted its first flight.<ref>Wagner 2009, pp. 125–26.</ref>

While other variants entered production during the 1960s, Saab continued the development of the more capable all-weather interceptor version of the aircraft, the JA 37. In 1970, Sweden's air defenses had been closely inspected and it was determined that the prospective JA 37 Viggen was highly suited to the role.<ref name="warwick 1261" /> In 1972, the Swedish government authorized the development of the fighter-interceptor variant to proceed, which was followed by several major contracts for the JA 37's further development.<ref name="ford 617" /> A total of five prototypes would be produced, four of which being modified AJ 37s and one being a sole pre-production JA 37 model, to test the control systems, engine, avionics, and armaments respectively.<ref name="warwick 1261" /> In June 1974, the first of these prototypes conducted its maiden flight; later that year, an initial order for 30 JA 37s was issued by the Swedish government.<ref name="warwick 1261" />

The JA 37 Viggen featured various changes from its predecessor, including revisions to the design of the airframe, the use of the more powerful RM8B powerplant, a new generation of electronics being adopted, and a revised armament configuration employed; the principal externally visible changes from most earlier variants were a taller tailfin and the underfuselage gunpack arrangement.<ref name = "fred 279" /><ref name="warwick 1260" /><ref>Chant 2014, pp. 458–59.</ref> The JA 37, in addition to its principal aerial combat mission, also retained a secondary ground-attack capability, and was better suited to low-level operations.<ref name="warwick 1261" /><ref name="chant 458" /> In November 1977, the first production JA 37 Viggen conducted its maiden flight.<ref name="chant 459" /> Operational trials for the new variant were conducted between January and December 1979, which resulted in the type being introduced to operational service that year.<ref name="chant 459">Chant 2014, p. 459.</ref><ref name= "warwick 1265" /> According to [[Flight International]], at the time of the JA 37's introduction, it was the most advanced European fighter then in service.<ref name="warwick 1260" />

[[File:Saab JA37C Viggen, Sweden - Air Force AN1117367.jpg|thumb|left|JA 37 Viggen at the [[Royal International Air Tattoo]] 1993]]
In April 1964, the Swedish government revealed its budget proposal for the Swedish Air Force, in which it had been envisioned that 800 or more Viggens would be produced, which was in turn intended to allow all other combat aircraft then in service with the Swedish Air Force to be replaced with this single type.<ref>[https://www.flightglobal.com/pdfarchive/view/1964/1964%20-%201127.html "World News: Over 800 Viggens."] ''Flight International'', 23 April 1964, p. 630.</ref> However, a combination of [[inflation]] and other factors eventually reduced the total number of aircraft manufactured to 329.<ref name="bomber 247" /> By 1980, up to 149 JA 37 Viggens were projected to be built, and the line to be closed within the decade as the Swedish aerospace industry changed focus to the impending Saab JAS 39 Gripen, the Viggen's eventual replacement.<ref name= "warwick 1260" /> Over time, advances in computing, such as the [[microprocessor]], had enabled greater flexibility than the physical configuration of the Viggen, so further development of the Viggen platform was not viewed as cost-effective.<ref>Eliasson 2010, pp. 87, 229.</ref> In 1990, production of the Viggen ceased and the final aircraft was delivered.<ref>Forsberg 1994, p. 220.</ref><ref name = "Eliasson 82">Eliasson 2010, p. 82.</ref>

In May 1991, a [[Swedish krona|SEK]] 300-million program to upgrade 11 AJ37, SF37 and SH37 Viggens to a common multirole variant, designated AJS37, was announced. Amongst the changes involved, interchangeable armaments and sensor payloads were implemented in addition to the adoption of new mission planning and threat analysis computer systems. The onboard ECM systems were also improved.<ref name="bomber 247" /> Specifically, the implementation of a new stores management system and [[MIL-STD-1553]] [[serial communication|serial]] [[bus (computing)|data bus]], similar to that used on the newer JAS 39 Gripen, allowed for the integration of the [[AIM-120 AMRAAM]] air-to-air missile; an upgraded Ericsson PS-46A radar was installed, and a new tactical radio. On 4 June 1996, the first upgraded prototype JA37 Viggen performed its first flight.<ref name="upgrade flies" />

In 1996, according to Swedish air force material-department chief General Steffan Nasstrom, the various upgrades performed to the Viggen since its introduction had "doubled the effectiveness of the overall system".<ref name="upgrade flies">Jeziorski, Andrzej. [https://www.flightglobal.com/news/articles/saab-flies-upgraded-viggen-fighter-12677/ "Saab flies upgraded Viggen fighter."] ''Flight International'', 19 June 1996.</ref>