Tail codes are markings usually on the vertical stabilizer of U.S. military aircraft that help identify the aircraft's unit and/or base assignment. This is not the same as the serial number, bureau number, or aircraft registration which provide unique aircraft identification.

A tail code (often confused with a tail number) refers to specific markings, usually on the vertical stabilizer, that identify an aircraft's organizational assignment rather than its unique individual identity. In civil aviation, the "tail number" is the registration (like N12345 in the U.S.), but in military aviation, "tail code" has a much more specific meaning. For the U.S. Air Force, for example, a two-letter tail code often identifies the aircraft’s home base or wing—such as "WA" for Nellis Air Force Base or "ZZ" for Kadena Air Base in Japan. These codes are designed to be easily read by ground crews and other pilots to quickly identify which unit a plane belongs to during large-scale operations. For the U.S. Navy, tail codes identify the specific Carrier Air Wing (CVW) assigned to an aircraft carrier. This system allows for efficient logistical tracking and helps maintain a clear chain of command and origin. While the tail number is like a car's license plate, the tail code is more like a fleet logo or a regional identifier that tells a story about the plane's current mission and "home" unit.