An amphibious aircraft or amphibian is an aircraft that can take off and land on both solid ground and water. They are typically fixed-wing, though amphibious helicopters do exist as well. Fixed-wing amphibious aircraft are seaplanes which are equipped with retractable wheels, at the expense of extra weight and complexity, plus diminished range and fuel economy compared to planes designed specifically for land-only or water-only operation. Some amphibians are fitted with reinforced keels which act as skis, allowing them to land on snow or ice with their wheels up.
A Canadair CL-415 amphibian with retractable wheels
Vickers Viking - an early amphibian.
replica of Osa's Ark - a Sikorsky S-38 used to explore Africa in the 1930s.
Italian Air Force Piaggio P.136 during takeoff retracting the wheels that make it an amphibian.
A fixed-wing aircraft is a heavier-than-air flying machine, such as an airplane, which is capable of flight using aerodynamic lift. Fixed-wing aircraft are distinct from rotary-wing aircraft, and ornithopters. The wings of a fixed-wing aircraft are not necessarily rigid; kites, hang gliders, variable-sweep wing aircraft, and airplanes that use wing morphing are all classified as fixed-wing aircraft.
A Boeing 737 airliner is an example of a fixed-wing aircraft
The fixed wings of a delta-shaped kite are not rigid
Children flying a kite in 1828 Bavaria, by Johann Michael Voltz
Le Bris and his glider, Albatros II, photographed by Nadar, 1868