This paper focuses on the development and performance of an aluminium prototype bonnet for the Saab 9-3. The first part describes how the bonnet was re-engineered in order to meet the functional demands. The study reveals that when considering these criteria the aluminium bonnet behaves equally well as the steel version and the target, to gain a 50% weight reduction, is met. The second part deals with the results of the performance tests by Saab. These tests give a good indication of the behavior which can be expected for the aluminium bonnets during service of the vehicle.