Purpose – This project analyses whether there are correlations between the level of NOx emissions and characteristic engine parameters within typical flight phases. --- Methodology – A representative selection of the most used engines is determined. Based on the data obtained, correlations between engine parameters and nitrogen oxide emissions are analysed by use of linear regressions methods. --- Findings – Through the analysis, four equations for determining NOx in the LTO-Cycle and in cruise flight were derived from an engine database, which can be used to estimate emissions in general. --- Practical implications – The results can be applied to recommend the preferred installation of certain engines. On the other hand, indications can be derived on how engines in use can possibly be improved regarding the reduction of NOx emissions. --- Social Implications – Preferring certain engine types due to lower NOx emissions could reduce aviation's contribution to global warming and environmental impacts. --- Originality – Apart from publications on nitrogen oxide emissions in aviation in general, there are yet no such well-founded comparisons in this context between the various engine types currently in use.