What defines a CAT 1 aircraft?

The defining characteristic of a CAT 1 aircraft is its maximum takeoff weight, which is 12,500 lbs or less. This classification is significant because it determines the level of air traffic control services that will be provided, as well as the types of airports and approaches the aircraft is eligible to utilize. Aircraft in this category are typically smaller general aviation airplanes and may include various types of propulsion systems, not limited to jets or multi-engine designs.

The other choices focus on aspects like engine type or specific configurations, which do not universally apply to all aircraft within this weight class. Thus, the maximum takeoff weight criterion is the most relevant factor in defining a CAT 1 aircraft.