What are the two types of organic fibers commonly used for covering aircraft?

The correct answer identifies cotton and linen as the two types of organic fibers commonly used for covering aircraft. Cotton has been a traditional fabric for aircraft covering due to its strength, flexibility, and easy handling properties. It is known for absorbing moisture, which can be beneficial in maintaining a stable structure under various environmental conditions. Linen, derived from the flax plant, also offers similar advantages, such as durability and a smooth finish conducive to aerodynamics.

Both cotton and linen are considered organic fibers since they are derived from natural plant sources. These characteristics make them suitable for use in applications where lightweight and good tensile strength are required. Moreover, their ability to be painted and doped with protective coatings makes them particularly useful in aircraft fabric covering.

While the other options include synthetic fibers or materials that are less commonly associated with traditional aircraft covering, cotton and linen have a historical significance and continue to be recognized for their practical qualities in aviation.