Which factor is NOT typically included in a discussion about aircraft performance?

In the context of aircraft performance discussions, population density is not a typical factor considered. Aircraft performance generally revolves around metrics directly related to the aircraft's operation, such as fuel consumption, engine efficiency, and flight capabilities.

Fuel burn is crucial as it determines the operational cost and range, playing a significant role in flight planning and efficiency assessments. Engine response time affects the aircraft's ability to react to control inputs and conditions during flight, influencing safety and maneuverability. Airspeed endurance is about how long an aircraft can sustain its speed before running out of fuel, which is essential for planning flight duration and distance.

Population density, on the other hand, refers to the number of people living in a specific area and does not directly influence the intrinsic performance characteristics of an aircraft. Therefore, it does not belong in the performance analysis of an aircraft.