According to Federal Aviation Regulation: except when necessary for takeoff or landing, no person may operate an aircraft below the following altitudes:
- Lower than minimum altitudes that will allow an aircraft to make an emergency landing without risking persons or property on the ground.
- Over congested areas: congested area of a city, town, or settlement, or over any open air assembly of persons, an altitude of 1,000 feet above the highest obstacle within a horizontal radius of 2,000 feet of the aircraft.
- Over other than congested areas: an altitude of 500 feet above the surface, except over open water or sparsely populated areas. In those cases, the aircraft may not be operated closer than 500 feet to any person, vessel, vehicle, or structure.
- Helicopters: may be operated at less than the minimums prescribed in the paragraph b or c of this section if the operation is conducted without hazard to persons or property on the surface. In addition, each person operating a helicopter shall comply with any routes or altitudes specifically prescribed for helicopters by the Administrator.