a, b, HONO slant columns from TROPOMI (rectangles) and nearly synchronized (± 15 minutes) aircraft CU-DOAS (dots), for Rabbit Foot fire (a) and Watson Creek fire (b). The fires source locations are indicated by the red points (source: https://firms.modaps.eosdis.nasa.gov/). c, d, Comparison between TROPOMI and aircraft RHN as function of plume age (Methods), respectively for (a, b). TROPOMI pixels delineated by grey lines in (a, b) are used for the comparison, and correspond to unambiguous detections of both HONO and NO2 with SCDs>2xretrieval uncertainty (other pixels are considered not suitable for comparison). The two aircraft traverses of the plumes are plotted separately. Aircraft measurements more than 5 km away from the satellite pixels are not considered. Error bars correspond to systematic uncertainties on RHNs.