With the increase in the air traffic, reducing the aviation environmental impact is the key challenge of the community. This has called for more research in the area of using alternative fuels which will reduce the greenhouse gas emissions and which can provide similar or better environmental performance. This work presents a preliminary design methodology of a mid-range single aisle commercial aircraft using Hydrogen as fuel which is stored in an integrated tank in the fuselage. The iterative design process was achieved by using overall aircraft design approach through the FAST-OAD open-source software. This study describes the models used for a first approximation of structural and insulation weight of liquid Hydrogen (LH2) tank and fuel boil off computations. It then presents the impacts of an LH2 storage system on the overall aircraft design with an emphasis on the centre of gravity (CG) travel and the additional fuselage length necessary to accommodate the LH2 tank. An additional parametric study has also been carried out to understand the effect of some design parameters on overall design. Finally, an environmental study has been conducted to evaluate the direct emissions of this aircraft in operation. The only emissions that result from the combustion of hydrogen are nitrogen oxides (NOx) which were evaluated using the Boeing Fuel Flow Method (BFFM2) and water vapor (H2O) which was evaluated based on the fuel burned. As a result of this study significant reduction in NOx and CO2 emissions as compared to existing design are envisaged, thus showing the promising potential of Hydrogen fuelled aircraft.