Ultralight aircraft, in the U.S., are those light aircraft (The FAA calls them vehicles) that carry one passenger, weight no more than 254 pounds,
carry no more than five gallons of fuel, have a maximum speed of no more than 63 mph, and stall at a speed no greater than 27 mph. Period. No other qualifications.
However, it is estimated that 80-90% of all ultralights, in the U.S., exceed at least one of these requirements. Usually, they weight too much and fly too fast. These are called "fat" ultralights and are really illegal aircraft.
