This paper addresses the evaluation of the key reliability indicators for gas-pumping aggregates at compressor stations in the natural gas transmission system, based on mathematical modeling of aging processes and the recovery of equipment characteristics. The main factors influencing the system's operation and the reliability of equipment at the current level of system management are the volume of reserves and their structure. These factors may change either due to more rational use and distribution of costs for the creation and development of the system or through an increase in these costs. Therefore, the issue of reliability is, in essence, a techno-economic problem. Thus, the research problem includes analyzing the operational characteristics of gas-pumping aggregates to identify the causes of deviations in actual repair cycles from standard ones, applying a stochastic approach to evaluating the reliability parameters of gas-pumping aggregates at compressor stations, and mathematically modeling the influence of repair service parameters on the main economic indicators of the gas transmission system. To achieve this goal, it is proposed to determine the approximating deviations of parameter functions and derive assessments of the element’s resource. However, the application of approximating functions has significant drawbacks, as forecasting machine states and using corresponding formulas complicates the forecasting process. Therefore, after selecting and calculating the coefficients of any approximating expression, it should be transformed into a defined function, for which a forecasting mechanism is developed. This is the only way to use a broad class of approximating expressions with relatively lightweight mathematical support for forecasting. The proposed method of forecasting gas-pumping aggregate resource was tested under the conditions of the compressor stations of the “Soyuz” and “Urengoy-Pomary-Uzhgorod” pipelines in the context of a comprehensive multifactor experiment conducted at gas transportation system facilities in Ukraine. This allowed for the prediction of reliability trends of gas-pumping aggregates at compressor stations, which ultimately determines the potential to meet consumers' gas demands. To maintain the reliability indicators of the elements in the gas transportation system, it is recommended to optimize their maintenance procedures. Significant improvement of the quality of repair work at this stage, under current conditions, is technically unfeasible and economically unjustifiable.