We studied the altitudinal movements of eight radio-collared female Alpine chamois Rupicapra rupicapra in the Swiss Alps to investigate how air traffic and environmental factors affect daily movements and medium-term altitudinal displacements in winter. Average altitude was often similar during periods of several days depending mainly on snow cover. Daily altitudinal movements occurred at all altitude levels and seemed to be affected more by local topography and habitat structure than by current environmental conditions. In individuals that were above the timberline in the morning, and thus were potentially exposed to air traffic, the first aircraft of a day could induce a downward movement, and a high intensity of air traffic (i.e. many aircraft during most of the day) affected the altitudinal difference that was covered during the whole day. After a downward movement the chamois returned to higher altitudes within a day and the following night, confirming their preference for the open pastures above the timberline. Two groups of chamois that were exposed to different intensities of air traffic, did not differ in their altitudinal movements, indicating a weak effect of aircraft. The daily energy costs of altitudinal locomotion were not considerably increased. We estimate that, on an average winter day, the energy costs of locomotion were not increased by more than 0.1% of the field metabolic rate (FMR) due to aircraft. However, a combination of deep snow and very intensive air traffic may result in a much higher increase in the energy expenditures on certain days. Further reasons for this ambiguous influence of aircraft are discussed.