When altitude increases, which aircraft aspect does NOT directly require change?

As altitude increases, the primary influences on flight characteristics and performance stem from changes in air density and temperature. In this context, passenger seating arrangement does not directly require adjustment because this aspect is largely independent of flight dynamics and performance influenced by altitude. The seating arrangement is primarily concerned with comfort and safety for passengers rather than the operational capabilities of the aircraft.

In contrast, flight speed, aerodynamic configuration, and flap position are all critical factors that are directly affected by changes in altitude. For instance, as altitude increases, the thinner air requires adjustments in flight speed to sustain lift and maintain performance; pilots may need to operate at higher true airspeeds to maintain the same indicated airspeed. Aerodynamic configuration, which includes aspects like the wing design and surface area, may also need to be optimized for different altitude conditions to ensure efficient airflow and performance. Flap positions are adjusted to manage lift and drag during takeoff and landing, and these adjustments are crucial as altitude changes can affect the aircraft's approach and landing performance.

Therefore, as altitude changes, whereas other aspects necessitate modification for safe and efficient flight, the passenger seating arrangement remains unaffected in terms of immediate operational requirements.