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The saturated hydraulic conductivity (K_s) is an essential parameter for modeling water and chemical transport in the vadose zone. Since in situ measurements of K_s are complex and time‐consuming, indirect methods that are dependable, fast, and inexpensive with regard to assessing magnitude and spatial variability in K_s at the field scale are needed. In situ measurements of air permeability (k_{a,in situ}) may fulfill these criteria. In this study, a portable insertion‐type air permeameter was used to measure k_{a,in situ} in the Ap and B horizons at five agricultural field sites in Denmark with soil types ranging from sand to sandy loam. Around 100 k_{a,in situ} measurements were performed within 2 d at each field site. The data showed spatial correlation in k_{a,in situ} at three out of five sites, with correlation distances between 30 and >120 m. On the basis of additional laboratory measurements on large, undisturbed soil samples …