I’m certain most here already know this, but I didn’t see it referenced and thought I’d offer a refresher for those operating in the USA.
Over cities and towns, the limit in 1000’ unless a landing area is nearby. In sparsely populated areas, the limit is 500 feet around persons or vehicles, vessels or structure.
If the pilot doesn’t see any of these, they could easily be below 500. BTW, even a fence counts as a structure; this rule keeps pilots from “legally” flying under bridges and power lines. Oh and helicopters can do anything
FAR 91.119 Minimum safe altitudes; general
Except when necessary for takeoff or landing, no person may operate an aircraft below the following altitudes:
(a) Not relevant here
(b) Over congested areas – Over any 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.
(c) Over other than congested areas – An altitude of 500 feet above the surface except over open water or sparsely populated areas. In that case, the aircraft may not be operated closer than 500 feet to any person, vessel, vehicle, or structure.
(d) Helicopters – Helicopters may be operated at less than the minimums prescribed In paragraph (b) or (c) of this section