Radio control airplanes nearly always refers to toy planes designed to be controlled remotely using some sort of steering and guidance system. They are popular toys amongst both children and adults, and are available in a wide variety of styles.
Originally, radio control was devised as a method during World War II to navigate missiles into dangerous locations without putting the operator in harm's way. The technology never took off, however, and was virtually abandoned by the end of the war.
Most radio controlled devices use an analog control system, where a small pulse is sent from a handheld unit and received by the model. The model then interprets the width of the pulse to indicate what direction, and to what degree, it should move. Servos in the model airplane then rotate, causing the plane to change direction. Recently, more expensive systems have begun using digital controllers and receivers, which are much more reliable, and have integrated fail-safes in case of signal loss.
Controllers for radio control devices come in different levels of complexity. Some may have be simple controls, allowing for forward, left, right, up, and down directions. Others may include a throttle as well, allowing for speed to be varied.
Radio control planes are built from different materials, including various types of wood (balsa being the most common), simple plastics, and carbon fibers. They can cost as little as $90, or as much as $5000. Radio control planes can range in power from simple two-stroke engines up to larger four-stroke engines. Sizes can vary from just over a foot (30cm) wingspan to a full ten to twelve feet (3-4 meters). The average radio control plane will last 10-20 minutes in the air, flying at speeds ranging from 30mph (48km/h) to 200mph (322km/h).
There are a number of hobbyist clubs for radio control airplane enthusiasts, found in virtually every nation on earth. The level of commitment taken by enthusiasts ranges as much as every other aspect of radio control airplanes, with some buying pre-made airplanes and meeting occasionally to fly them, and others building planes from scratch and entering races and other competitions.