Embodiments provide systems, methods, and computer program products for optimizing cruise altitudes for multiple aircraft. The embodiments may be used for optimizing cruise altitudes of multiple aircraft on multiple flight paths and/or system capacity by an operator and/or an air navigation service provider. According to exemplary embodiments, a first set of optimum initial cruise altitudes are established for a plurality of aircraft. Weather conditions at the first set of optimum initial cruise altitudes are accounted for to establish a second set of optimum initial cruise altitudes. Direction of flight at the second set of optimum initial cruise altitudes is accounted for to establish a third set of optimum initial cruise altitudes. Any conflicts between aircraft at the third set of optimum initial cruise altitudes are detected. When a conflict is detected, the conflict is resolved to establish a fourth set of optimum initial cruise altitudes.