The invention relates to a system and a method for calculating flight predictions of an aircraft in which an intermediate prediction horizon is defined between the flight phase and the leg. This horizon, that is called vertical section, is defined such that the limit conditions that are applicable to it, for example the target speed, target altitude, characteristic altitude and maximum end-of-section distance, are valid for the entire vertical section. Thus, it is not necessary, in calculations to check the compatibility of the flight parameters with the applicable constraints, to arbitrarily select the constraint that must be given priority. Furthermore, this intermediate level architecture allows for a greater modularity of the prediction management software and therefore a greater factorization of the developments and greater ease of maintenance.