The next generation of aircraft with a large number of effectors will require advanced methods for control allocation (CA) to compute the effectors' commands needed to follow the desired objective while respecting associated constraints. Currently, the main challenge of the CA is to achieve low enough computation time with a deterministically optimal result for a real-time application. In this paper, at first, we cast the CA as a nonlinear convex programming problem which depicts the desired objective function subject to three-axis moment demands and the limits of effectors' movement; then we develop a computationally tractable method for real-time application on the CA of the aircraft flight control system. The method can analytically and deterministically give one optimal solution for the CA and prove this optimal solution to be guaranteed within a certainly maximal computation time. Numerical testing results based on Boeing C-17 transport aircraft and Lockheed-Martin tailless fighter models demonstrate that the method is effective in terms of its computational efficiency, accuracy, and reliability.