Aircraft plywood is produced by using glues of the thermosetting, synthetic resin type. The quality requirements for plywood to be used in aircraft are much more exacting than for industrial plywood in general. Aircraft plywood meets MIL-P-6070B. The mill specification requires that the plywood be tested for general condition of boards, deviations of thickness, moisture content, tensile strength of wood, gluing strength, bending test, torsion test, immersion test and boiling test. Plywood is factory certified. MIL-P-6070B is laminated in hot press with waterproof glue. 90° grain runs with 8′ direction. 45° grain runs diagonal (use for spar facing). Approximate weight is based on 4′ X 8′ sheets.