Categories of Model Airplanes
Flying models are usually divided into three categories. Free-flight airplanes fly free of any on-ground attachments. Control-line model planes are controlled by users through a wire stretching from the aircraft to a handheld unit. Radio-controlled models are operated by a pilot through transmitting radio signals to a receiver inside the aircraft.
ARF Models
Instead of building a flying model aircraft from scratch, entry-level users can buy kits that are completely or nearly completed. These are known as ARF or "Almost ready to fly" models.
Static-scale Model
Static-scale models---the simplest type of model airplane---mostly come unassembled in kits. Assembly requires the use of glue, rubber cement or epoxy. Hobbyists often paint and apply decals to these models. Plastic, fiberglass, paper or balsa wood are used in their construction.
Popularity
Static-scale model airplanes are popular among children and airplane model collectors. They're small-scale versions of life-sized aircraft. These airplanes can also resemble imaginary aircraft, especially those featured in movies or designed as space aircraft. The most popular scale of static-scale models is 1:72, meaning one life-sized aircraft has the same length as 72 of its static-scale models.
Materials
Model airplanes are made of many substances, including plastic, diecast metals and composite materials such as graphite. Composite materials are normally only used to make higher-end, radio-controlled versions. Balsa wood is an inexpensive, commonly used material for aircraft models because it's lightweight and easy to carve.