Measurements of NO and O3 are presented from 13 aircraft flights made over the Pacific Ocean in the autumn of 1983 during one phase of the NASA Global Tropospheric Experiment (GTE). All of the flights were made between 15° and 42°N and from the coast of California to west of the Hawaiian Islands. Within the upper marine boundary layer the median daytime mixing ratio of NO was near 1 part per trillion by volume (pptv). As well, values of NO less than 10 pptv were often observed up to altitudes near 6 km. Thus for the location and season of the measurements, a net photochemical destruction of O3 would be anticipated for the boundary layer region and to altitudes of 2–3 km. At higher altitudes of 7–11 km in the free troposphere, larger mixing ratios and greater variability were usually observed for NO. Both features are consistent with observed examples of injection of NO and O3 from the lower stratosphere and with the injection of NO from towering, electrically active, cumulonimbus clouds.