This paper presents the results of the joint aircraft design project "The Green Freighter" that dealt with the investigation of hydrogenfueled freighter aircraft. This included conventional as well as blended-wing-body (BWB) aircraft designs. Within the scope of the project the Preliminary Aircraft Design and Optimization program PrADO was extended and applied to analyses of conventional and unconventional freighter aircraft designs. The investigations show that hydrogen as aviation fuel is feasible. Rising energy prices will make air transport more expensive than today, but hydrogen is a potential alternative fuel that keeps air traffic possible even if low-priced kerosene is no longer available. In addition, air traffic could become more environmentally friendly. Hydrogen-fueled regional freighter aircraft have up to 5% smaller maximum takeoff masses and consume about 10% less energy than the kerosene reference version despite their up to 7% higher operating empty masses. The installation of large hydrogen tanks using the full fuselage cross section is significantly superior to an installation of removable tanks with smaller diameter. An unmanned freighter can use the cockpit volume for hydrogen storage and further helps to optimize the design. The investigations of the hydrogen-fueled BWB designs show possible savings of about 6.5% in take-off mass, which is predominantly due to a 66.5% lower fuel mass. The combination of necessary minimum aircraft size and low fuel mass causes a low wing loading. In effect, the BWB designs cannot make use of their theoretically very high aerodynamic performance during cruise flight.