Correction coefficients to reduce the production of exhaust emissions to standard-day conditions for ambient temperature and humidity were developed for two classes of aircraft turbine engines. Correlation and multiple regression methods were used in the analysis of emission measurements recorded from two turbine engines, operated under naturally occurring environmental conditions, starting in the winter and continuing through the summer season. Correction factors were established for the emission index (EI) and power index (PI) for carbon monoxide (CO), total hydrocarbons (THC), and nitrogen oxides (NOx) for each of five engine power conditions of idle, approach, cruise, maximum continuous, and takeoff. Ambient temperature produced the dominant effect on all gaseous emissions. EI and PI for THC required the greatest magnitude of ambient temperature correction factors. Humidity had a significant secondary effect on the generation of NOx). The effects of barometric pressure were within experimental error for the minimal range of pressures encountered. The correction coefficients established from a TF30-P1 engine data base were determined to be applicable for correction of JT8D engine emissions. The temperature and humidity effects on the generation of emissions are now considered to have been a major source of variability of measurements from past investigations.