This thesis work focuses on the analysis of the direct operating costs of a supersonic civil transport aircraft powered by liquid hydrogen. As we know, the correct assessment of direct operating costs from the early stages of a space project is of primary importance, but this is neither easy nor immediate, since its accurate estimation requires the use of a substantial database not always available (especially for supersonic aircraft). In addition to this, it is also necessary to analyzed the impact that a new technology such as liquid hydrogen (a technology widely studied and debated and that will certainly be used on aircraft in the coming decades) has on costs.