What is the altitude for the Southern Control Area (SCA) as defined in high-level airspace?

The Southern Control Area (SCA) is defined within the context of high-level airspace as starting at 18,000 feet above sea level (ASL) and extending upwards. This altitude, known as the transition altitude in many jurisdictions, is significant because it marks the point at which aircraft are typically required to operate under Instrument Flight Rules (IFR) if they are flying at higher altitudes.

At and above this level, aircraft operate in airspace that is generally less congested, where air traffic control can manage larger distances between aircraft, providing greater efficiency and safety for high-altitude operations. Thus, the definition reflects regulatory standards that are established for safe and efficient air traffic management in controlled airspace.

Other options suggest different altitudes which do not correspond with the established definition of the SCA. For example, altitudes below 18,000 feet do not fall under high-level airspace, which is exclusively above this threshold. Additionally, altitudes like FL230 or FL270 specify levels above the 18,000 feet minimum but do not encompass the full definition of the SCA.