The company was incorporated on February 18, 1948, with headquarters at No. 1, Buenos Aires street in Bilbao and a capital of 100 million pesetas. Its first president, Elias Ugartechea Isusi from December 1946 had permission to perform non-scheduled domestic air services, which transferred to the new company.
On May 1, 1948 Aviaco received its first aircraft, Bristol 170 Freighter three Mk 21, which began operations from Bilbao to Madrid and Barcelona. In 1949 Aviaco established his base of operations at the airport of Madrid-Barajas, starts with the Canaries routes, Alicante and Badajoz and also joins the IATA.
In 1950 it was named president Joseph Manor Montes, added 9 aircraft SE.161 Sud-Est Languedoc and create routes between Madrid and Seville, Jerez, Madrid-Lugo-Santiago de Compostela, Madrid-Alicante-Oran and Barcelona-Brussels-Amsterdam. In 1951 starts the routes of the Cantabrian coast, initially covering correspondence Madrid-Lugo-Santiago de Compostela, Bilbao-Zaragoza-Barcelona, which later split into several sub-paths, and also created the route Bilbao-Bordeaux and Madrid-Vitoria.