At approximately 1030 central time, an Aerotek Pitts S-2A was damaged when it lost part of a wing while maneuvering near Grand Prairie Municipal Airport. The pilot and his passenger were not injured. The pilot said he was performing a power-off stall and the airplane entered a spin. As he recovered from the spin, a four-foot section of the bottom left wing separated. The pilot was able to fly the airplane back to GPM.