The growing attention to the reduction of climate-altering emissions in the aeronautical sector is driving research toward More-Electric Aircraft (MEA) architectures and the use of hydrogen-powered Fuel Cells for the generation of electrical power on board. Although the bleedless Environmental Control System (ECS) and PEM Fuel Cells have been extensively studied and characterized separately in the literature, a system-level analysis that concretely evaluates their integration in terms of mass, aerodynamic drag, and hydrogen consumption along a realistic mission profile is lacking. In this work, a modular framework of a bleedless ECS (featuring a Three-Wheel Air Cycle Machine configuration) and a black-box model of a PEMFC cell are developed, implemented within the OpenMDAO framework.