What characterizes a "Part 91" operation in aviation?

A "Part 91" operation in aviation is primarily characterized as general aviation operations that are not conducted for compensation or hire. This means that the activities under this regulation do not involve commercial services or the transport of passengers or cargo for payment. Instead, they encompass various non-commercial flying activities, such as private flying, recreational flying, and other aviation operations that do not seek profit.

Understanding this definition helps clarify the broader context of how aviation is regulated. Part 91 provides flexibility in operating procedures for private pilots, allowing them to fly aircraft under certain conditions without the stringent requirements and oversight that come with commercial operations. This aspect is significant as it sets the foundation for many flying activities that prioritize safety, pilot discretion, and personal use.

The other options pertain to different categories of aviation operations governed by different regulations and are not applicable under Part 91.