Lightweight unmanned aerial vehicles (UAVs) are increasingly used in applications such as search and rescue, plant inspection, and the delivery of small goods. While their size and scope often allow for more accessible regulatory path-ways, these systems still pose safety risks and must undergo appropriate development and safety assurance processes, often guided by simplified regulations like the EASA “Specific Operations Risk Assessment (SORA)” scheme. In the future, even autonomous navigation in certain mission phases might become desirable, posing novel safety challenges and further increasing complexity. This paper presents a model-based approach to UAV development that supports both system design and safety assessment in an integrated and scalable workflow, easy enough to handle for smaller companies, and agile enough to cope with varying requirements. Emphasizing rapid iterations and adaptability to evolving mission requirements, the method enables early validation and feedback through continuous refinement of system and algorithm models, complemented by safety analysis and simulation. System architecture, functional behaviour, and safety artefacts are modelled in SysML and connected to safety arguments using GSN. We present selected solution com-ponents, like degradation cascades and validation through simulation in more de-tail. A UAV use case demonstrates how this approach supports efficient development cycles and safety case generation, making it suitable for SMEs developing autonomous airborne systems.