This paper investigates the effects using high lift zero-net mass-flux Co-Flow Jet (CFJ) active flow control airfoil for aircraft control surfaces with plain flaps and with no flap. The goal is to reduce the size and weight of conventional aircraft control surfaces and save energy expenditure. Two-dimensional simulation of NACA 0012 airfoil used as a control surface is conducted for parametric trade study using a Reynolds-averaged Navier-Stokes (RANS) solver with Spalart-Allmaras (SA) model. A 5th order WENO scheme for the inviscid flux and a 4th order central differencing for the viscous terms are used to resolve the Navier-Stokes equations. The 2D numerical studies indicate that the CFJ airfoil for aircraft control surfaces with a plain flap can dramatically increase the lift coefficient and aerodynamic efficiency simultaneously compared with the conventional control surface with the same size of flap and deflection angle. CFJ airfoil control surface shows great potential to substantially reduce the size and weight of conventional aircraft control surfaces with high control authority. A series of trade study is done based on NACA0012 airfoil for control surface. The CFJ airfoil is modified from the baseline NACA0012 airfoil by translating the upper surface downward by 0.1%C. A constant deflection angle of 30° is used. The final preferred configuration has the flap length of 35%C, deflection angle of 30°, injection location at 2%C from leading edge, injection slot size of 0.5%C, and suction slot right upstream of the flap with the size twice larger than the injection size. The final trade study is to investigate the effect of injection jet momentum coefficient Cµat 0.05, 0.15, 0.25. The lower Cµvalue of 0.05 is the most energy cost effective to increase the lift coefficient. Comparing with the baseline airfoil with the same flap size and deflection angle, at sideslip angle of 0°, the case of Cµ=0.05 of the final configuration achieves a lift coefficient increase by 106.4% from CL=1.09 to 2.25 at very low power coefficient of 0.0285. At the same time, it substantially reduces the drag by 67.17%. All these compound effects result in an increase of aerodynamic efficiency(including CFJ power consumption) by 232.2%. In other words, while the CFJ control surface substantially increases the lift, it simultaneously reduces the net energy cost in a dramatical manner. This even does not count the additional benefit due to the reduced control surface size and weight Finally, CFJ airfoil with no flap is also simulated at injection jet momentum coefficient Cµ=0.05, 0.10, 0.15, 0.20, 0.25 and 0.30. The result shows that the maximum lift coefficients of 3.048 (an increase of 114%) is achieved at Cµ=0.30 with a reduced drag. The aerodynamic efficiency of the flapless control surface is not studied in this work and will be reported in future. The results indicate that flapless control surface may be a feasible option.