Seatbelts are nearly as old as powered flight.The need to restrain aircraft occupants became obvious as soon as unusual attitudes and inverted flight were realized by pioneer aviators. Whether simple lap belts or sophisticated harnesses, any model's aircrew perch is improved by well represented seatbelts.
Most modern plastic kit seats have molded on interpretations of the genuine article, but these typically lack detail and fail to impart the look of a functional belt lying across a seat. While skillfull painting can help improve the effect, nothing can surpass a purpose made strap to simulate the real thing.
This presentation is just one suggestion of how to create your own belts and harnesses in your next modeling project by employing Fine Grain Milliput - Two-Part Epoxy Putty.