What is the horizontal radius required for altitude restrictions over congested areas?

The correct radius for altitude restrictions over congested areas is indeed 2,000 feet. This requirement is based on aviation safety regulations designed to minimize risk in populated regions.

In congested areas, aircraft need to maintain a higher level of safety due to the proximity of people and structures on the ground. The 2,000-foot radius is established as a buffer zone to ensure that even in the event of an emergency or unexpected situation, any descent or maneuvering by the aircraft will not endanger persons or property on the ground. The regulation aims to strike a balance between operational efficiency for aircraft and the safety of the communities below.

In practice, this means that if an aircraft is above a dense urban area, it must stay at least 2,000 feet above the highest obstacle within a horizontal distance of 2,000 feet from the aircraft's projected flight path, enhancing overall safety through these operational constraints.