The task of aircraft flight route search in severe environment of flight is discussed in the article. This task is related to multi-criteria optimization tasks types and requires significant timing budget and computation resource to solve it. This task solution method with the use of cellular automaton on 3D lattice gas model was discovered in the work. The main difference of the discovered method consists in elaboration of lattice gas cellular automaton 3D model features, development of a new approach to the calculation of changing probability of cell position and determination of rules of adjacent elements identification and development of new rules of transfer into them. The developed method allows constructing the model with the different level of detail that allows regulating the decision search time and searching the decisions in separate environmental areas.