Light aircraft is an aircraft with a maximum gross takeoff weight of less than 600 kilograms (1320 pounds; with some exceptions for seaplanes), a maximum airspeed in level flight of 120 knots (222 km/h), either one or two seats, a fixed-pitch propeller, and a piston engine. These aircraft require only a sport pilot certificate, not a private or recreational pilot certificate as with other certificated aircraft.
The U.S. definition of an LSA is similar to most other countries' definitition of "microlight" or "ultralight" aircraft. These definitions are typically less restrictive, not limiting airspeed or the use of variable-pitch propellers. The FAA also has its own definition of ultralight aircraft which is much more restrictive and does not have an equivalent in some other countries.
Certain certificated aircraft, such as the original Piper Cub, meet the definition of light-sport aircraft, and can be operated by sport pilots.
Several designers and manufacturers of experimental aircraft kits are working to develop models that are compliant with the light-sport aircraft rules. Unlike traditional experimental aircraft, completed light-sport aircraft may be offered for sale.