WCET analysis is a key activity in the development of safety critical real-time systems. Whether upper bounds on WCETs are obtained using static analysis or measurements, the confidence on the compliance of a system with its temporal requirements directly depends on the confidence on these estimations. Static WCET analysis based on abstract interpretation takes benefits from its formal foundations. However, it also strongly depends on the correctness of the underlying models. We hereby show how we have validated the version of the data flow static analyser of OTAWA applied to the AURIX TC275 target processor.