Which regulation governs the limitations on flying after alcohol consumption?

The regulation that governs the limitations on flying after alcohol consumption is 91.17. This regulation establishes clear guidelines concerning the use of alcohol by pilots. Specifically, it prohibits pilots from operating an aircraft while under the influence of alcohol or within a certain time period after consuming alcoholic beverages, typically set at eight hours. This regulation aims to ensure the safety of flight operations by preventing impairment due to alcohol consumption.

In contrast, the other options refer to different aspects of aviation regulations. For instance, 91.33 deals with the use of alcohol or drugs in general, but it does not specifically address the duration after consuming alcohol before flying. Regulation 91.105 pertains to the requirements for the maintenance of aircraft, and 91.515 relates to the specific operating limitations for altitude and atmospheric conditions, none of which deal directly with alcohol consumption before flying. Thus, 91.17 is the precise regulation that outlines the critical limitations concerning alcohol use for pilots.