The TheMa4HERA project takes on the huge challenge of on-board thermal management that comes with the introduction of hybrid electric power and propulsion systems in Regional and Short and Medium Range aircraft. This will be achieved through development, design and testing at TRL 5 of wide range of innovative technologies from Air Supply, to Air Conditioning, Systems Thermal Management to Cabin Air Distribution. Whereas today’s thermal management systems need to handle a heat dissipation of about 35-50kW, tomorrow’s hybrid electric regional aircraft will have to handle heat dissipation in the range of 300 to 1.000kW! With a consortium composed out of all key aerospace players in the market of thermal management, this project will address almost all currently known thermal management technologies. Multiple two-way interactions loops with TRA-01 will be established integration requirements and feedback constraints and validation results, to allow for further aircraft architecture optimization iterations. Through the development of a full digital twin, the project will be able to simulate and optimize component level requirements for any given aircraft architecture. This architecture will be taken from the EXACT project, adjusted and refined throughout the project, to eventually reflect the final Hybrid Electric Aircraft architecture. The project will validate and demonstrate its results in a full-scale demonstration test facility at Fraunhofer IBP. With the further refined models, that will be available by then, the project will also be able to calculate the achievements towards the Expected Outcomes, in particular the environmental footprint. The Communication, Dissemination and Exploitation actions will make sure that all necessary stakeholders will also be supportive to the EIS of the first Hybrid Electric Regional Aircraft relying on TheMa4HERA thermal management technologies.