The point (altitude) at which, as the indicated airspeed decreases with altitude, it progressively merges with the low speed buffet boundary where pre-stall buffet occurs for the airplane at a load factor of 1.0 G.

• A. Aerodynamic Ceiling
• B. Absolute Ceiling
• C. Stall Boundary
• D. Low-Speed Ceiling

Answer: (A)

The key idea is that at high altitude the air is so thin that the speed you’d need to stay in level flight at 1 g moves toward the point where the aircraft begins to buffet at low speed. The aerodynamic ceiling is the altitude where the speed required for steady, level flight at 1 g effectively merges with the low‑speed buffet boundary. Beyond this point, there isn’t a safe margin to fly at 1 g without encountering pre‑stall buffet, so practical level flight becomes impossible regardless of throttle or power.

This is different from the absolute ceiling, which is about the maximum altitude at which the airplane can stay in level flight given its climb capability, not about the low‑speed buffet limit. It’s also different from the stall boundary itself, which marks the low‑speed limit at 1 g; the aerodynamic ceiling is where that boundary is reached due to increasing altitude.