Atmospheric ammonia (NH3) has been shown to impact the environment and threaten both human and animal health, especially in heavily populated urban areas, yet to date there remains a paucity of direct measurements. Recent studies have suggested that ammonia may be generated as a byproduct of fossil fuel emissions due to highly active catalytic converters in light-duty gasoline vehicles. To investigate this relationship, an airborne miniature Chemical Ionization Mass Spectrometer (miniCIMS) was used to directly measure atmospheric ammonia and combustion reaction products in the Southern California LA Basin, during the 2015 NASA Student Airborne Research Program (SARP). The temporal variability in measured ammonia, and the relationship to combustion efficiency will be compared to mobile ground-based measurements from the NASA DISCOVER-AQ campaign, and implications of the findings will be discussed
