Description of the maximum forces produced by flying animals is important for understanding general limits to lift and power production, but such limits can be difficult to identify unequivocally. We compared two methods (incremental addition of supplemental mass, and asymptotic load-lifting) to determine potential methodological differences in estimates of maximum flight performance for the bumblebee Bombus impatiens. Relative to the estimates derived from asymptotically increasing loads, incremental mass addition systematically underestimated maximum lifting capacity by ~20%, and also yielded a spurious intraspecific allometry of maximum vertical force production. Bumblebees lifted on average of 53% of their body weight, but the overall allometry of muscle mass-specific vertical force production was slightly but significantly negative.