Which statement is true regarding Subpart 121.Z applicability?

• A. It applies to multi-engine aircraft.
• B. It applies to aircraft with seating capacity 9 or fewer.
• C. It applies to single-engine aircraft.
• D. It requires MTOW over 8618 kg.

Answer: (C)

Subpart 121.Z is defined by the aircraft’s engine configuration, focusing on single-engine airplanes. The safety and certification considerations for a single-engine aircraft are different from those of multi-engine machines, so the rules in this subpart are tailored to that category. That’s why the statement that it applies to single-engine aircraft is the correct one.

The other criteria—being multi-engine, having a seating capacity of nine or fewer, or a maximum takeoff weight above a certain threshold—don’t determine Subpart 121.Z’s applicability. Those factors relate to other regulatory divisions or definitions, not to this subpart’s scope.