Ultralight aviation is a segment of aviation that is permitted in the United States of America by the FAA as long as certain weight and fuel capacity restrictions are observed. The governing regulation is FAR 103, and allows single pilot aircraft of less than 5 gallons fuel capacity to fly over unpopulated areas during daylight hours.
Most ultralights can be flown safely only under ideal weather conditions.
No licence or training is required by law, but training is highly advisable. Conversely ultralights are simple to fly. A novice can be soloed with radio assistance from a qualified instructor in 2 hours for some ultralight types (powered parachutes). Other types require much more extensive instruction and practice.
There are several classes of aircraft (officially termed "vehicles" by the FAA)