Volcanic CO₂ emission rate data are sparse despite their potential importance for constraining the role of magma degassing in the biogeochemical cycle of carbon and for assessing volcanic hazards. We used a LI-COR CO₂ analyzer to determine volcanic CO₂ emission rates by airborne measurements in volcanic plumes at Popocatépetl volcano on June 7 and 10, 1995. LI-COR sample paths of ∼72 m, compared with ∼1 km for the analyzer customarily used, together with fast Fourier transforms to remove instrument noise from raw data greatly improve resolution of volcanic CO₂ anomalies. Parametric models fit to background CO₂ provide a statistical tool for distinguishing volcanic from ambient CO₂. Global Positioning System referenced flight traverses provide vastly improved data on the shape, coherence, and spatial distribution of volcanic CO₂ in plume cross sections and contrast markedly with previous results based on traverse stacking. The continuous escape of CO₂ and SO₂ from Popocatépetl was fundamentally noneruptive and represented quiescent magma degassing from the top of a magma chamber ∼5 km deep. The average CO₂ emission rate for January-June 1995 is estimated to be at least 6400 t d⁻¹, one of the highest determined for a quiescently degassing volcano, although correction for downwind dispersion effects on volcanic CO₂ indicates a higher rate of ∼9000 t d⁻¹. Analysis of random errors indicates emission rates have 95% confidence intervals of ∼±20%, with uncertainty contributed mostly by wind speed variance, although the variance of plume cross-sectional areas during traversing is poorly constrained and possibly significant.