What federal Aviation Regulation applies to all pilots?

FAR Part 91 is the correct regulation that applies to all pilots, regardless of the type of flight operation they are conducting. This part outlines the general operating and flight rules which govern the use of aircraft and cover a broad range of aviation operations.

Part 91 includes regulations about pilot certifications, aircraft operations, and responsibilities during flight, ensuring that safety and compliance are maintained in all aviation activities. It forms the baseline for pilot and operator privileges and limitations. Since it applies universally to pilots, every individual operating an aircraft under U.S. jurisdiction must adhere to its provisions, making it a critical part of a pilot's knowledge base.

The other options represent specific regulatory frameworks that apply to particular types of operations. FAR Part 121 is applicable to scheduled air carriers and air transportation, while FAR Part 135 addresses commuter and on-demand operations. FAR Part 141 is focused on pilot schools and training programs. Each of these regulations is tailored to specific aspects of aviation and does not apply universally to all pilots, highlighting why FAR Part 91 is the foundational regulation for all pilots.