The Brazilian commercial aviation industry has been intensively debated in recent years, especially regarding congestion and infrastructure bottlenecks. One of the structural factors that have been identified as potential inducers of the problems currently observed in the industry is increasing the concentration of the network of airlines at the expense of coverage throughout the national territory. The present work aims to study this degree of concentration in Brazil, through the modeling of indicators based on the Herfindhal Hirschman Index (HHI). We developed a set of theoretical bounds concerning alternative types of network structure - point-to-point versus hub-and-spoke - in order to provide a methodology to identify possible airports hubs. This methodology is most appropriate to the reality of the Brazilian case than the traditional approach of the Federal Aviation Administration (FAA). Additionally, we promoted a comparative analysis of results from different approaches, contrasting them with the results of a survey conducted by a panel of experts. The final results show a better performance of the modeling proposed here, in contrast to the indicators suggested by the FAA.