With the growth of urban areas, the areas adjacent to airports are becoming densely inhabited, causing a big problem known as encroachment. The encroachment occurs when a significant portion of the population is submitted to the adverse effects of noise, even outside the areas of restricted use established by the airport zoning. The metric used for the airport zoning in many countries and in Brazil is the DNL (Day Night Level). This metric is associated to the average sound energy produced by all aeronautical events during a period of 24 hours, with weighting of 10 dB(A) during the night. However, the use of DNL for airport zoning can lead to different results for noise levels, daytime and nighttime, depending on the seasonality of airport activity in those periods. The paper proposes a study of alternatives for the airport zoning based on the Brazilian Standard ABNT/NBR 10151. It also presents a comparative analysis between the indices of encroachment through a Geographic Information System for two Brazilian airports: the Congonhas Airport and the Recife Airport, aiming to adjust the municipal zoning to the airport zoning.