Explain the term "no-fly zone."

The term "no-fly zone" refers to an area where unmanned aircraft systems (UAS), among other aviation operations, are restricted or prohibited from flying. These zones are often established for safety, security, or environmental reasons. For example, no-fly zones may exist around airports to prevent interference with manned aircraft, over populated areas for safety concerns, or around sensitive installations for security. By enforcing such restrictions, authorities aim to ensure the safety of people on the ground and the integrity of airspace.

The other options describe different scenarios: high wind conditions can affect flight safety but do not establish airspace restrictions; recreational flying areas are intended for leisure activities but do not necessarily denote restrictions; and regions where UAS can fly unrestricted refer to locations that do not have any imposed flying limitations. These details help to clarify the distinct nature of a no-fly zone in the context of airspace regulation.