By contrast, the US FAA has a separate definition of ultralight aircraft defined in Federal Aviation Regulations. Aircraft falling within the US ultralight specifications are extremely lightweight (less than 254 pounds if powered, or 155 pounds if unpowered), are intended for manned operation by a single occupant, have a fuel capacity of five US gallons (about 19 litres) or less, a maximum calibrated airspeed of not more than , and a maximum stall speed of not more than . Ultralight aircraft in the US do not require pilot licensing, medical certification, or aircraft registration.