Atmosphere-breathing electric propulsion (ABEP) is a type of electric propulsion system that uses the atmosphere as a propellant source instead of a stored reservoir. This technology is still in its early stages, but holds the promise of providing a clean, efficient, and sustainable propulsion system for spacecraft, enabling very low Earth orbit (VLEO) mission scenarios. To optimise the ABEP technology, accurately simulating air-based plasma chemistry plays a crucial role. In this paper, an air-based global model (GM) is presented that includes a detailed chemistry model for the various reactions that are involved in ABEP applications. The model’s goal is to forecast the performance of a cathode-less RF plasma thruster under various pressure levels and species concentrations that are typical of VLEO missions. The GM was exploited to map the performance of a fictitious ABEP based on a cathode-less RF thruster in order to assess its feasibility in VLEO. The numerical model is promising as a tool for the design of ABEP systems and for the preliminary optimization of mission scenarios.