The objective of this paper is to present a Simulink model-based approach for simulation and optimization of a robust satellite data unit (SDU) able to deliver safety and nonsafety aeronautical mobile satellite services, including capabilities to operate in an airborne network. For this purpose, analysis and modeling of the main avionics system signals and data traffic to be treated in an SDU were performed. The main contribution here is the design of the SDU data traffic model, which integrates different simulation models in avionics systems, such as automatic dependent surveillance-broadcast, aircraft communications addressing and reporting system, and in-flight connectivity for future implementation and optimization, thus allowing the characterization of a device onboard in a modular framework. To conclude, this paper describes a modeling and analysis tool aimed at providing the aviation industry with the means to reduce the amount of equipment onboard (and thus the weight of aircraft to reduce fuel consumption) and fulfill passengers' demand for connectivity. Finally, note that this modeling is a step further toward the development of a device that ensures greater operational safety and ease of repair and maintenance.