The problem of optimal investment in the aircraft engine manufacturing industry has become increasingly urgent in recent years. Insufficient financing of the enterprises of the industry leads to massive reductions and a slowdown in the innovative development of the industry. The relevance of the chosen research area is determined by the importance of ensuring the sustainable functioning of enterprises in the market, increasing their capacities and achieving targets, including those that are considered strategically important for the development of the industry as a whole. The purpose of the study is to develop the authors’ methodological approach, which makes it possible to assess the financial position of an enterprise and determine the missing amount of financial investments for its stable functioning. We propose a new approach to determining the optimal amount of necessary financial investments in the aircraft engine manufacturing industry for its successful functioning with the help of zoning enterprises according to the degree of financial stability based on the analysis of some indicators of the financial condition of each enterprise and identifying deviations of these indicators from the standard values. Based on the data of the financial statements of enterprises affiliated to UEC (JSC United Engine Corporation), the financial position of the enterprise was assessed on the basis of sample indicators, and the analysis of the state program “Development of the aircraft industry”, in particular the subprogram “Aircraft engine manufacturing”, in the field of benchmarks of these programs and their budget component. The results obtained in the course of the study, presented in the form of funds necessary for the normal functioning of the industry and allocated for the same period from the federal budget, are compared. As a result, it can be concluded that the amount of budgetary allocations is insufficient for the development of the aircraft engine manufacturing industry in the Russian Federation. As a result of the study, the lack of funds for enterprises located in the “grey” and “red” zones were identified. The essence of the methodological approach of optimal investment in the aircraft engine manufacturing industry is the possibility of its application in practice to optimize state programs in the field of aircraft industry development, in particular, the aircraft engine manufacturing of the Russian Federation.