Real transportation fuels are complex mixtures of a variety of hydrocarbon components. Predicting NOx formation in practical combustors burning real fuels is usually made with the assumption that the NOx submodels developed and tested for small hydrocarbon combustion are applicable to mixtures of large hydrocarbons as found in real fuels. Additionally, NOx data are scarce for flames of real fuels. The aims of the current study are (i) to provide reliable NOx data in flames of a typical jet fuel, and (ii) to test our capability to predict these data by combining a recently proposed HyChem reaction model of jet A combustion (Xu et al., 2018) with the NOx submodel of Glarborg (2018). Specifically, NOx concentrations were measured in stretch-stabilized premixed flames of methane and Jet A (POSF10325) from fuel lean to rich conditions and of ethylene at a fuel-rich equivalence ratio. This range of stoichiometries allows both thermal NO and prompt NO pathways to be tested. The results show reasonably good agreement between the experimental data and model predictions for all flames tested, although the model appears to underpredict NOx concentrations in the Jet A flames under fuel rich conditions. Sensitivity analyses were conducted to illustrate the influence of the reaction pathways and flame boundary conditions on NOx predictions. The analyses also suggest that additional prompt NO reaction pathways may play a role in flames of large hydrocarbons. (C) 2019 The Combustion Institute. Published by Elsevier Inc. All rights reserved.