This paper considers dynamic modeling and control of a flexible kiteplane used for wind-energy harvesting. Each component of the kiteplane is modeled separately and is then constrained to the other components using the null-space method. The flexible wings are modeled as thin plates with bending and torsional stiffness. An unsteady aerodynamic model is included to increase the fidelity of the simulation under transient conditions. A proportional-integral-derivative (PID) attitude control law is implemented that uses the direction cosine matrix (DCM) directly and proportional-integral (PI) control is used to track a desired tether reel-in rate. Numerical simulation of the closed-loop system demonstrate the kiteplane's ability to harvest wind energy.