In recent work carried out in the LAPLACE laboratory, a model of PEM fuel cells in variable operating conditions was proposed and investigated [1] [2]. This model allows predicting with satisfactory results the polarization curves of PEM single cells which operate in a defined operating range. First results seem also promising if we want to extend the validity domain of this model to other operating condition ranges. The purpose of our work is to study the behaviour of this model when it is applied to a PEM fuel cell stack operating in typical aeronautical conditions in order to be able to estimate its performance. Particular attention will be paid to low pressure functioning. An experimental database is created using the Design of Experiments method and is then exploited to parametrize the model. First modelling results will be presented and analysed.