Federal Aviation Regulations state: Except when necessary for takeoff or landing, no person may operate an aircraft below an altitude allowing, if a power unit fails, an emergency landing without undue hazard to persons or property on the surface. Over any congested area of a city, town, or settlement, or over any open air assembly of persons, no lower than 1,000 feet above the highest obstacle within a horizontal radius of 2,000 feet of the aircraft.
Over uncongested areas, no lower than 500 feet above the surface. Over open water or sparsely populated areas, aircraft may not be operated closer than 500 feet to any person, vessel, vehicle, or structure.
Helicopters. Helicopters may be operated at less than the minimums listed above if the operation is conducted without hazard to persons or property on the surface.