An efficient parallel hybrid solver consisting of the method of moments (MoM) with higher-order basis functions (HOBs) and physical optics (PO) is proposed for the analysis of complicated phased array antennas on electrically very large platforms. The higher-order MoM is hybridized with PO by iterating the MoM voltage matrix. The block-partitioned scheme for the large dense MoM matrix combined with the process-cyclic scheme for the PO discretized triangles is designed based on message passing interface (MPI). The parallel method is able to achieve excellent load balance and high parallel efficiency, and provides a solution with reasonable accuracy for solution of large on-board antenna problems. Numerical examples are presented to demonstrate that the proposed method can efficiently handle challenging realistic problems with a maximum dimension greater than 1000 wavelengths. © 2006 IEEE.