Ultralight Vehicles: An Ultralight vehicle, according to Federal Aviation Regulation 103.1 is a vehicle that: a) Is used or intended to be used for manned operation in the air by a single occupant. b) Is used or intended to be used for sport or recreation only. c) Does not have any U.S. or foreign Airworthiness Certificate; and d) If unpowered, weighs less than 155 pounds; or e) If powered: 1) Weighs less than 254 pounds empty weight, excluding floats and safety devices intended to be deployed in a potentially catastrophic situation; 2) Has a fuel capacity not eceeding 5 U.S. gallons 3) Is not capable of more than 55 knots calibrated airspeed at full power in level flight; and 4) Has a power-off stall speed which does not exceed 24 knots calibrated airspeed. Notice they never call the thing an aircraft??? Always a "vehicle".