Production. Airplane manufacture, general. Thousands of sheet metal plane parts are formed daily in the drop hammer department of North American Aviation, Incorporated at Inglewood, California. Hemp rope and the rubber in the mold on the press are used to snub and control the impact of the hammer. This plant produces the battle-tested B-25 ("Billy Mitchell") bomber, used in General Doolittle's raid on Tokyo, and the P-51 ("Mustang") fighter plane, which was first brought into prominence by the British raid on Dieppe