Homebuilt and experimental aircraft are constructed by hobbyists who have not pursued aviation as a professional activity. Most of these amateur aircraft are designed from scratch, previously drafted plans, or from assembly kits. Homebuilt aircraft builders may register their projects as "experimental" under the Federal Aviation Association (FAA) or similar regulatory bodies relevant to their country; however, the amateur builder is restricted from distributing the model for profit. In the United States, the amateur-aircraft builder can obtain a repairman's certification on the registered aircraft, which allows the holder to conduct routine maintenance checks, repairs, and inspections without reporting to a third party.
Generally, homebuilt aircraft only requires a modest amount of construction. Amateur aircraft builders use a variety of materials to construct the body, including plywood, fabric-covered wood, fiberglass, composites, metal and aluminum frames. The engines are often the same used in certified aircraft made from prominent manufacturers, such as Continental, Jabiru, Rotax, and Lycoming; however, a small percentage of amateur builders use converted automobile engines to help reduce the cost. The majority of amateur builders prefer specifically designed aircraft engines for their performance and reliability.
In 1910, Alberto Santos-Dumont, a pioneer of homebuilt aircraft, offered the first no-cost construction plans of his aircraft model entitled the "Demoiselle" in the same-year edition of Popular Mechanics. However, the first amateur-built aircraft model offered for sale was the "Baby Ace" during the late 1920s. In 1955, Canada showcased its first homebuilt aircraft. It is currently displayed at the Canada Aviation and Space Museum. In 1924, amateur-built aircraft became popular in the United States with the advent of the National Air Races hosted in Dayton, Ohio. The National Air Races required amateur-aircraft to have a useful load weighing in at around one hundred fifty pounds, and the engines should measure eighty cubic inches or less.
The interest in homebuilt aircraft dwindled until Charles Lindbergh completed his transatlantic flight between 1929 and 1933. Many aircraft designers, builders, and pilots taught themselves during this period, which resulted in a high accident rate. As a result, the public outrage enforced the regulation of amateur-building, including its standards on design, stress analysis, engineering, use of aircraft quality hardware, and testing. Therefore, the upsurge in amateur-building disappeared from the scene. In 1946, Goodyear reintroduced the National Air Races, which included a class of aircraft equipped with 200 cubic inch and smaller engines. This special midget class rapidly spread across the United States, which resulted in the popular demand for acceptable standards to allow personal use of amateur-built aircraft. The United States and Canada obliged to these calls, which allowed amateur-built aircraft to be flown for recreational use according to specific standards and limitations.
Without the imposition of regulatory restrictions, amateur-aircraft builders introduced their own innovative designs and construction techniques, such as the canard design and the RV series. As the decades passed and technology improved, amateur-aircraft kits started to include advanced components, such as autopilots and navigational instruments. It was not until the 1970s and 1980s that the amateur-aircraft kit market began to stagnate, because of litigation and regulations. This force the remaining surviving companies to only distribute older, proven designs until more recently when less restrictive regulations for amateur-built aircraft allowed a handful of manufacturers to develop newer and innovative designs. In fact, modern amateur-built aircraft can even outperform certified production aircraft that fall into their class, such as the Lancair Propjet, a 4-seated kit with a pressurized cabin and turboprop engine.
Historically, homebuilt aircraft has a less than an impressive safety record, especially when compared to certified general aviation aircraft. In 2003, the rate of amateur-aircraft accidents was an estimated 21.6 per 100,000 flight hours. This overshadows the 6.75 to 100,000 flight hour ratio of general aviation accidents. The Federal Aviation Administration (FAA) has struggled to control the accident rate for amateur aircraft in the United States. The government agency has raised awareness that homebuilts account for roughly ten percent of the general aviation fleet, but twenty-seven percent of all accidents. The FAA has offered primary flight training from any CFI willing to provide instruction in an experimental aircraft. Similarly, the United States National Transportation Safety Board drew conclusions that homebuilt aircraft has an accident rate ranging between three to four times higher than the rest of the general aviation fleet, with almost ten percent of amateur-built accidents occurring on the first flight.