most often a recreational activity. Unmanned gliders A paper plane is a toy aircraft (usually a glider) made out of paper or paperboard. Model glider aircraft are models of aircraft using lightweight materials such as polystyrene and balsa wood. Designs range from simple glider aircraft to accurate scale models, some of which can be very large. Glide bombs are bombs with aerodynamic surfaces to allow a gliding flightpath rather than a ballistic one. This enables the carrying aircraft to attack a heavily defended target from a distance. Kite A kite is an aircraft tethered to a fixed point so that the wind blows over its wings. Lift is generated when air flows over the kite's wing, producing low pressure above the wing and high pressure below it, and deflecting the airflow downwards. This deflection also generates horizontal drag in the direction of the wind. The resultant force vector from the lift and drag force components is opposed by the tension of the one or more rope lines or tethers attached to the wing. Kites are mostly flown for recreational purposes, but have many other uses. Early pioneers such as the Wright Brothers and J.W. Dunne sometimes flew an aircraft as a kite in order to develop it and confirm its flight characteristics, before adding an engine and flight controls, and flying it as an airplane. Uses Military applications Kites have been used for signaling, for delivery of munitions, and for observation, by lifting an observer above the field of battle, and by using kite aerial photography. Science and meteorology Kites have been used for scientific purposes, such as Benjamin Franklin's famous experiment proving that lightning is electricity. Kites were the precursors to the traditional aircraft, and were instrumental in the development of early flying craft. Alexander Graham Bell experimented with very large man-lifting kites, as did the Wright brothers and Lawrence Hargrave. Kites had a historical role in lifting scientific instruments to measure atmospheric conditions for weather forecasting. Radio aerials and light beacons Kites can be used to carry radio antennas. This method was used for the reception station of the first transatlantic transmission by Marconi. Captive balloons may be more convenient for such experiments, because kite-carried antennas require a lot of wind, which may be not always possible with heavy equipment and a ground conductor. Kites can be used to carry light effects such as lightsticks or battery powered