We consider logical-probabilistic modeling of the reliability behavior of multilevel systems described by nonmonotone functions of the algebra of logic. A method is proposed for calculating the parameter of the flow of transitions to a subset of states specified by a nonmonotone function. An approach to calculating estimates of interval indicators of reliability, efficiency, and safety of multilevel systems on logical-probabilistic models is described. An example of calculating the indicators of the operational availability of a multilevel system with nonmonotone logical criteria for the transition between levels is given. The calculated values of indicators are compared with the results of Markov modeling.