As part of the Northern Wetlands Study (NOWES) in the summer of 1990, 30 flights were conducted with the National Research Council (NRC) Twin Otter research to quantify the spatial and temporal variations of CO2, H2O, and sensible heat fluxes over the Hudson Bay lowland. These consisted of two regional runs of approximately 100 km in length from James Bay to the Kinosheo Lake and 13-km runs in the form of ''L'' and grid patterns near the Atmospheric Environment Service (AES) tower in the Kinosheo Lake area. An examination of the average fluxes shows that day-to-day differences were larger than the spatial differences. Significant correlations were found between the fluxes of CO2, sensible heat and latent heat, and selected environmental characteristics, such as air temperature, vapor pressure deficit, surface temperature minus air temperature, and incident solar radiation, for different sections of the NOWES area. The presentation of the spatial variations of aircraft-based fluxes of CO2, sensible heat, and latent heat over a 13 km¿13 km area near Kinosheo Lake permits an evaluation of the spatial representativeness of the AES tower observations.