The development of safety-critical embedded systems presents some demands, such as low-level communication with hardware devices, uninterrupted operation in hostile environments and some restrictions such as memory size, processing power and, particularly, low power consumption. These systems require specific development methodologies, targeting the development of products with certified quality. This paper presents an approach named SAFE-CRITES, created to ease the certification of future products, also improving reuse in all developments steps (from the architecture to design and coding). A case study of a complex embedded system for guidance and control of an unmanned aircraft is presented, contributing to the evaluation of the proposed approach for real world applications.