WHILE IN CRUISE ALTITUDE EN ROUTE TO ATHENS, GA THE ENGINE QUIT. THE FLIGHT WAS LAST OBSERVED BY HUNTERS LOW OVERHEAD PRIOR TO COLLIDING WITH TREES. THE WITNESS DID NOT HEAR THE ENGINE RUNNING. THE COLLISION SEPARATED THE WING STRUCTURE AND THE AIRPLANE CRASHED INVERTED IN THE WOODS. THE WRECKAGE EXAMINATION FAILED TO DISCLOSE MECHANICAL PROBLEMS. RECONSTRUCTION OF THE FLIGHT ROUTE INDICATED THAT THE PILOT DID NOT HAVE ENOUGH FUEL. EN ROUTE ATTENTION TO ACTUAL FLIGHT TIME WOULD HAVE ALERTED THE PILOT OF THE NEED TO REFUEL PRIOR TO ATHENS.