In this paper we present a method for determining optimal routes along selected paths in a wireless mesh network based on an interference aware delay analysis. We develop an analytic model that enables us to obtain closed form expressions for delay in terms of multipath routing variables. A flow deviation algorithm is used to derive the optimal flow over a given set of routes. The model takes into account the effects of neighbor interference and hidden terminals, and tools are provided to make it feasible for the performance analysis and optimization of large-scale networks. Numerical results are presented for different network topologies and compared with simulation studies.