The main parameters are understood as: carrying capacity mг, range L and fuel efficiency qт, which largely determine the competitiveness of aircraft of this type, including military transport aircraft. The reason for the creation of modifications of transport category aircraft is the requirement for a constant increase in their flight performance by increasing the carrying capacity and range. Among the main goals of implementing such decisions there is an indispensable increase in the fuel efficiency of modifications, since the cost of fuel reaches 80 % of the cost of an airplane hour during operation. There are a number of models that make it possible to assess the influence of the weight and aerodynamic parameters of the airframe of the aircraft and the fuel performance of the power plant (specific engine consumption) on the integral indicator of the fuel efficiency of the modification at cruising mode and the average hourly fuel consumption at the certification stage, when all parameters of the airframe and engine are fixed and consideration of options is not possible. A new model is proposed for the stage of designing modifications, in which deep modification changes are made in the geometry of wing and in the power plant with various variants of their correlation and coordination. The parameters of new model: specific fuel efficiency – specific route productivity, in order to form the relative carrying capacity and relative range of action for the required specific fuel efficiency. An analysis of such dependencies showed: – with an increase in relative range L , fuel costs per flight also increase; – the adequacy of changes in route performance is observed only at L < 0.5. At L > 0.5 productivity is constantly decreasing, while the specific indicator of fuel consumption per unit of work increases exponentially; – if in the analysis we take into account the specific value of transport efficiency, that is, the characteristic “load – range” ( mп.н f L ), it becomes obvious that the most favorable (from the point of view of fuel efficiency) are relative ranges of 0,3 < L < 0,5. In this range L , not only acceptable fuel efficiency values are realized, but also the maximum value of the route performance, that is the main parameters for which modifications are developed.