Which of the following is not an aircraft category rating?

When considering the various categories under which aircraft ratings are classified, an aircraft category rating is a formal classification that affects how pilots are trained and what types of aircraft they are certified to operate. The ratings typically include airplane, helicopter, and glider, as these represent distinct types of aircraft with unique operating characteristics.

Airplanes are fixed-wing aircraft, helicopters are rotary-wing aircraft, and gliders are unpowered aircraft that rely on aerodynamics for flight. Each of these categories is recognized for pilot licensing and entails specific training, qualifications, and operational standards.

On the other hand, airships, while they are indeed a type of aircraft, do not fall under the primary categories of airplane, helicopter, or glider that are typically referenced in pilot licensing frameworks. Instead, airships are classified separately, often under lighter-than-air aircraft. This differentiation means they do not qualify as a standard aircraft category rating in the context of pilot certifications.

Thus, the correct choice indicates that airship is not a standard aircraft category rating when compared to the more commonly recognized categories.