considered two ways ahead: developing its own new models and/or buying licences to build trucks designed by another company. The outcome was that Avia purchased licences from the French Renault-Saviem company to build two types of truck. Series production of the new trucks began in autumn 1968. The larger vehicle was the Renault-SG 4 Super Galion (later Avia A30), and the smaller was the SG 2 Super Goelette (later Avia A15). The manufacture of the new models required new buildings as well as modernization of existing enterprises' premises. New buildings housing advanced equipment were built, and Avia became among the largest Czechoslovak vehicle manufacturers. Annual production reached 17,000 vehicles. Over the years the Avia models were continuously modernized. The displacement of the diesel engine increased from original 3.32 to 3.61 litres, and the new engines were fitted to nearly all Avia trucks. In 1983 the Avia A31 was developed from the Avia A30 model, and the Avia A15 (later A20) furgon was succeeded by the Avia A21 model. From 1974 to 1978 the A20, 30, and 40 models were modernized with smaller wheels, redesigned axles, new dashboard, enhanced cab interior, and other modernizations. In 1986, the Avia National Concern, including affiliated operations in Brno, Ivančice and Žilina was incorporated in a so-called "Industry Economical Unit" together with Praga, BSS, Metaz and Kutná Hora enterprises. As per 1 July 1988, a new state enterprise, Avia Concern, comprising Avia, Praga, BSS, and Dačické Strojírny. Concern enterprises were established in accordance with the State Enterprise Act. Avia Letňany, as the parent factory, made engines and cabs and assembled all the chassis. Part of the chassis was fitted with a platform-type superstructure and also vehicles with a furgon-type body were made there. The Brno, Ivančice and Žilina factories built superstructures for assembly on the chassis. The Kutná Hora factory made all types of axles for Avia vehicles. The major output of the Praga Concern Enterprise included truck and bus gear units and a number of other parts for the automotive field. The Dačické strojírny Concern Enterprise produced parts for car manufacturers. The body assortment was still growing: box bodies, isothermic box bodies, bodies including a cooling unit, assembly platforms, container bodies, dumpers, towing trucks, and other different bodies were made. The Avia chassis was also a base for the small buses built in Bulgaria, Yugoslavia and Hungary. In 1989 the concern was split into