An investigation has been conducted in the Langley Full-Scale Tunnel to evaluate the aerodynamic performance, stability, and control characteristics of the Advanced Technology Light Twin-Engine airplane (ATLIT). Data were measured over an angle-of-attack range from minus 4 degree to 20 degree for various angles of sideslip between minus 5 degree and 15 degree at Reynolds numbers of 2. 30 multiplied by 10**6 and 3. 50 multiplied by 10**6 for various settings of power and flap deflection. Measurements were also made by means of special thrust-torque balances to determine the installed propeller characteristics.