What horizontal distance from a built-up area deems an aircraft to be operated over it?

The correct answer is based on the regulations regarding the minimum horizontal distance an aircraft must maintain from built-up areas during flight operations. According to aviation safety regulations, specifically under Canadian aviation rules, an aircraft is required to operate at least 2,000 feet horizontally from any built-up area or assembly of persons on the ground. This regulation is in place to enhance safety and minimize risk to people on the ground in the event of an emergency or mechanical failure.

Choosing this distance ensures that there is ample space for the aircraft to maintain a safe altitude above populated areas, thus mitigating the potential for accidents involving the ground populace. The other distances mentioned in the options either fall short of the required separation or exceed what is deemed necessary for the safety protocols in place. Adherence to this 2,000-foot guideline is essential for ensuring both the safety of the aircraft operations and the well-being of individuals below.