Example methods and systems for determining a distribution of balloons based on population densities is provided. A method may include receiving information indicating a region divided into a plurality of horizontal bands of latitudes and a population density for one or more areas of the region. The method may also include associating the population density for a given area with a corresponding horizontal band of latitude in which the given area resides, and based on the population density associated with each horizontal band of latitude, determining a distribution of a plurality of balloons per horizontal band of latitude. The method may also include providing instructions to control the distribution of the plurality of balloons per horizontal band of latitude to remain in a trajectory substantially within a respective horizontal band of latitude.