In pursuit of cost-effective and sustainable space access, Dawn Aerospace is pioneering innovative launch systems. Their focus lies on a semi-reusable, two-stage-to-orbit launch vehicle, designed for horizontal take-off and landing. While current launch vehicles rely solely on rocket propulsion, the potential of airbreathing engines on the first stage is explored. Airbreathing engines offer increased fuel efficiency and utilize the incoming airflow as oxidiser. This study delves into the feasibility of integrating airbreathing propulsion into Dawn Aerospace's Mk-III vehicle, with a goal to reduce gross take-off mass while meeting mission requirements. Airbreathing engine types are evaluated, with ramjets and turbine engines emerging as primary candidates. Detailed design processes, including vehicle modeling, trajectory analysis, and optimization, are employed. The study reveals the potential of the ramjet concept which could have a lower gross take-off mass compared to fully rocket powered designs. Nevertheless, the application requires an improved vehicle design to obtain a feasible design.