Advanced Air Mobility (AAM) is an emerging market and technology in the aerospace industry. These systems are being developed to overcome traffic congestion. The current designs make use of Distributed Electric Propulsion (DEP): either fully electric or hybrid electric. The hybrid engine system consists of two power sources: prime movers, such as turbine engines, and batteries. The hybrid systems offer higher range and endurance compared with the existing fully electric systems. Hybrid-electric power generation systems for AAM have different mission requirements when compared to systems used in automobiles. Therefore, there is a particular need to model hybrid-electric systems and the development of control logic specifically for AAM aircraft. This thesis focusses on the modeling and design of control logic for hybrid-electric power plants for Advanced Air Mobility (AAM) applications. The developed model can assist in designing and optimizing the system as well as supporting the system architecture. These models can also help the testing and integration of hardware and software of systems and sub-systems, also known as software-in-the-loop and hardware-in-the-loop simulations. A state-space representation of the hybrid-electric system is created and validated with experimental results to facilitate the use of modern controls methods. A control law for the hybrid-electric system was also developed to meet the AAM aircraft mission requirement of generating the required electrical power and maintaining the State of Charge (SOC) of the batteries