A system approach to estimation of guaranteed safe operation of complex engineering systems is proposed. The approach is based on timely and reliable detection, estimation, and forecast of risk factors and, on this basis, on timely elimination of the causes of abnormal situations before failures and other undesirable consequences occur. The principles that underlie the strategy of the guaranteed safety of CES operation provide a flexible approach to timely detection, recognition, forecast, and system diagnostic of risk factors and situations, to formulation and implementation of a rational decision in a practicable time within an unremovable time constraint.