The Aircar is a roadable airplane narrow enough for driving in the flight configuration. Driving and model flight testing concentrated on issues beyond a first demonstrator Aircar. These include achieving a 70 m.p.h. power-off stall speed, required for certification, and driving in a crosswind. The results show that the aerodynamics of the winglet, must be considered for both modes and are critical to satisfactory “wing rock” characteristics. A satisfactory compromise is achieved by using the main landing gear oleo struts to maximize the lower winglet area in the air and to minimize it on the ground.