As the only mammals capable of powered flight, bats make efficient use of the aerosphere. Yet, our understanding of how bats use the three-dimensional air column is sketchy. By attaching miniaturised Global Positioning System tags to cave bats near a mountain ridge in Thailand, we show that these bats perform undulating ascending and descending flights in quick succession. Bats repeatedly used mountain slopes to ascend to altitudes of more than 550 m above the ground. We infer that mountain ridges are key habitat features for some openspace foraging bats, facilitating altitudinal movements which may aid effective foraging and navigation. Therefore, the development of wind farms along mountain ridges might lead to conflicts with the conservation of some open-space foraging bats.