How far must aircraft be separated from SUA and ATCAA below FL600?

The correct answer highlights the required separation distance between aircraft and Special Use Airspace (SUA) and Air Traffic Control Assigned Airspace (ATCAA) below Flight Level 600 (FL600) as being 3 miles. This distance is specified in aviation regulations to ensure safe separation and prevent potential conflicts between non-participating aircraft and operations occurring within these airspace types.

Special Use Airspace includes areas where activities such as military training operations take place, which may pose risks to civilian aircraft if they inadvertently entered the airspace. The 3-mile buffer serves as a precautionary measure to maintain safety.

In contrast, other distance options are not stipulated for this particular regulation, making them inappropriate for this scenario. Adhering to the 3-mile separation standard is critical for both ensuring safety and compliance with airspace regulations.