Weathering refers to wear and tear on a model airplane. This may be from the elements (e.g. sun-faded paint), or from operational wear. The actual weathering pattern will depend on the specific airplane, its maintenance, and where it was operated (e.g. dusty airfield). It's best to consult reference photos of the actual airplane, and look at them often while weathering the airplane. Careful application of weathering will greatly increase the realism of your model, and can turn it into a show-stopper.

Here are some typical weathering patterns and methods of applying them to your model:

Paint chipping occurs when parts of the paint layer get removed, to reveal the underlying bare metal. This often happens on heavily exposed or trafficked areas of the plane, e.g. wing walks, canopy frame edges and wing leading edges. Paint chipping can be simulated with silver paint and a fine brush, or a silver Prismacolor pencil. Another popular method is to paint a silver base coat, then apply the base color. While the base color is still somewhat wet, use masking tape to remove sections of the paint.

Gun smoke stains can be added with black pastel chalk dust applied with a fine brush (blow gently in the direction of airflow to remove the excess). Pastels are best applied over a flat (matt) surface, so if necessary first paint the model with a flat clear coat. The pastels will also need to be sealed with a clear coat. A convenient option that needs no sealer is to use an airbrush to make the stains. Airbrush (in the airflow direction) a fine line of highly thinned black paint.

Engine exhaust stains can also be added with black pastel chalk dust applied with a brush. To vary the effect, add some dark browns or grays on top of the black. The airbrush can be used very effectively here as well.

Pre-shading. Full-scale airplanes see lots of wear and tear in regular use. The surface skin panels often have uneven wear, with the center of the panels becoming lighter than the edges. Pre-shading can be used to mimic this effect on models. The panel lines on the model are darkened first, before applying any color coats. Highly thinned black or darkened base color is airbrushed along the panel lines, and around the raised surface detail. The lines can be a bit uneven, as real wear is not even. The pre-shading is then over-sprayed with the base color, without completely covering the pre-shaded lines. This technique can be used on any model with visible panel lines. If the model is molded in dark plastic, you may need to apply a light-colored primer coat before pre-shading.

Panel Fade is uneven wear of an airplane