Why do aircraft wings have a swept design?

The design of aircraft wings with a swept configuration primarily aims to delay the onset of critical Mach number and thus increase the aircraft's maximum speed. As an aircraft approaches transonic speeds, airflow over the wings can begin to reach Mach 1, leading to shock waves that can dramatically affect performance, efficiency, and control. By sweeping the wings backward, the airflow over the wings is effectively managed; this alters the relative Mach number experienced by the wing. This design feature allows the aircraft to fly faster before encountering the adverse effects of shock waves, making swept wings particularly advantageous for high-speed jet craft, where maximizing speed and performance is crucial.

The other options present some potential benefits associated with wing design but are not directly related to the primary reason for a swept wing configuration in high-speed aircraft. Therefore, the swept wing design stands out as a critical element for enhanced speed and performance in modern aviation.