For prototypes and flight-test designs, see experimental aircraft or x-planes.

In the United States, Experimental Aircraft is defined by the FAA as an aircraft that can be made and flown by anyone. These aircraft currently comprise approximately 25% of the general aviation fleet and are constructed with varying materials and techniques.

The Experimental Aircraft designation is supported by the Experimental Aircraft Association. These aircraft are at least 51% constructed by a private individual, rather than by a licensed aircraft manufacturer. Among fliers in the US, these aircraft are commonly called "homebuilt".

These aircraft are built from materials in one of three categories: rag and tube, metal, or composite materials (fiberglass, carbon fiber, etc.). The first category, describes a building method where the aircraft's superstructure is built using welded steel tube covered with a dacron fabric. This fabric is then painted to stiffen it. The second category, metal, describes the common all aluminum aircraft. Examples of this kind of aircraft include the Vans RV series of 1 & 2 place kits. Finally, the most recent addition to the fleet is made from composites. This category is notable for its designs employing body curvature which would be impossible with the other materials.

The largest airshow in the world is the EAA's (Experimental Aircraft Association) annual airshow in Oshkosh, Wisconsin, which takes place in late July and early August. Another annual event is the Sun N' Fun Fly In which occurs in the early spring in Lakeland, Florida. Both of these events are called "Fly Ins" as many people fly their homebuilts and other aircraft into the airport hosting the show. Both events last a week. Takeoffs and landings at these shows number in the thousands.