How high must airplanes maintain altitude above a built-up area or open air assembly of persons?

Airplanes must maintain an altitude of 1000 feet above the highest obstacle within a horizontal distance of 2000 feet from the aircraft when flying over a built-up area or an open air assembly of persons. This regulation is implemented to ensure safety by providing a sufficient margin between the aircraft and any potential obstacles, such as buildings or structures, which could pose a hazard during flight.

Maintaining this altitude helps to mitigate risks associated with engine failure or other emergencies, allowing pilots ample altitude for recovery maneuvers. The horizontal distance criterion ensures that the aircraft remains safely clear of obstacles that may be nearby, reducing the likelihood of a collision.

Understanding this specific requirement is crucial for commercial pilots, as it reflects both safety considerations and regulatory compliance necessary in their operational environment.