Final answer:
In the U.S., general aviation aircraft flying VFR above 12,500 feet MSL typically squawk 1200, unless directed otherwise. Above 18,000 feet MSL (Class A airspace), flights are IFR, and specific transponder codes are assigned by air traffic control.
Step-by-step explanation:
The question refers to the VFR transponder code for aircraft flying above 12,500 feet. In the United States, general aviation aircraft flying under Visual Flight Rules (VFR) above 12,500 feet MSL (Mean Sea Level) up to and including 17,999 feet MSL are typically required to adjust their transponder to squawk 1200, unless otherwise instructed by air traffic control. However, above 18,000 feet MSL, which is Class A airspace, all flights are IFR (Instrument Flight Rules), and specific transponder codes are assigned by air traffic control. The transponder code is a four-digit number that is broadcasted by the aircraft’s transponder and helps in identifying and tracking the aircraft on radar. It's essential for managing air traffic and ensuring the safety of all flights. Since the question specifically asks about operations above 12,500 feet, it is important to note that visibility and cloud clearance requirements are also more stringent at altitudes above 10,000 feet MSL to ensure safety when flying VFR.