What is the primary advantage of a swept wing design?

The primary advantage of a swept wing design is that it delays the onset of supersonic flow. This design helps to manage airflow over the wings as an aircraft approaches the speed of sound. By angling the wings backward, the wing's effective critical Mach number is increased, meaning the aircraft can fly faster before experiencing shock waves that can increase drag and lead to flow separation.

This characteristic is crucial in high-speed flight, as it allows the aircraft to maintain more stable and efficient performance as it approaches transonic speeds. Aircraft with swept wings can also achieve better aerodynamic efficiency, allowing them to handle the stresses associated with high velocities while delaying adverse effects like shock-induced drag.

In the context of the other options, while swept wings do influence lift and maneuverability, and may not directly reduce drag at all speeds, their primary and most significant advantage is how they handle airflow dynamics as speeds increase, effectively delaying the transition to supersonic flow.