Which regulation covers operating requirements for commuter and on-demand operations?

The regulation that specifically addresses operating requirements for commuter and on-demand operations is 14 CFR Part 135. This part of the Code of Federal Regulations outlines the safety standards, operational limits, and requirements for air carriers that operate under these types of services.

Part 135 is designed for smaller operations, such as charter flights or air taxi services, and it establishes various operational protocols including crew training, maintenance, and safety measures that must be adhered to in order to ensure a high level of safety for passengers and cargo.

In contrast, 14 CFR Part 121 primarily regulates larger airline operations which involve scheduled air transportation, while Part 125 applies to commuter and on-demand operations as well, but it focuses on larger aircraft with a passenger capacity of over 20 seats or a payload capacity exceeding 6,000 pounds. Part 380 relates to the consumer protection regulations for charter air services, rather than the specific operational requirements. Therefore, 14 CFR Part 135 is the appropriate regulation for commuter and on-demand operations, making it the correct answer.