In this study we implemented a comprehensive analysis to validate the GOES WFABBA active fire detection product using approximately 400 ASTER and ETM+ scenes at 30 m resolution as our primary validation data. Our analyses are focused in the Conterminous United States and Brazilian Amazonia, two important areas of fire activity in the Americas. We characterize the major sources of omission and commission errors which have important implications for a large community of fire data users. We found that at the 50% detection probability mark (p<0.001), WFABBA requires four times more active fire area than it is necessary for MODIS Thermal Anomalies (MOD14) to achieve the same probability of detection, despite the 16× factor separating the nominal spatial resolutions of the two products. Approximately 95% of all fires sampled were omitted by the WFABBA instantaneous product whereas this omission error was reduced to 38% when considering the 30 minute interval of the GOES data. Commission errors were highly dependent on the vegetation conditions in particular across Amazonia, with the larger commission errors (approximately 35%) estimated over regions of active deforestation. Nonetheless, the vast majority (> 80%) of the commission errors were indeed associated with recent burning activity where scars could be visually confirmed in the higher resolution data. The overall non-fire related commission errors were estimated as only 3% for both the Conterminous United States and Brazilian Amazonia.