Which FAA regulation corresponds to the requirements for airline operating procedures?

The regulation that aligns with the requirements for airline operating procedures is found in 14 CFR Part 121. This section of the Code of Federal Regulations specifically addresses the rules governing the operation of domestic, flag, and supplemental air carriers and commercial operators. It includes detailed requirements regarding aircraft operations, maintenance, crew training, and operational procedures, which are critical for ensuring the safety and efficiency of airline operations.

In contrast, the other parts mentioned serve different purposes. Part 139 focuses on certification of airports serving scheduled air carriers, detailing standards for airport facilities and services. Part 145 covers repair stations and the maintenance requirements for aircraft and aircraft components. Part 91 contains general operating and flight rules, typically for private and recreational flying rather than commercial airline operations.

Thus, the correct choice highlights the specific regulatory framework guiding airline operators, emphasizing their operational procedures to maintain safety in commercial aviation.