Why is 90 degrees the maximum angle of intercept for course intercepts?

The reasoning behind 90 degrees being the maximum angle of intercept for course intercepts is that angles greater than this could lead to a situation where the aircraft begins to track the course in the opposite direction. When an intercept angle exceeds 90 degrees, it can create confusion in navigation, as the aircraft might not be aligned correctly to follow the intended course. This misalignment can result in the aircraft veering off course rather than intercepting it correctly, increasing the risk of navigational errors and complicating the flight path.

Keeping the angle at or below 90 degrees ensures that pilots can make a smooth transition onto the desired course without encountering the risks associated with sharp turns and potential reversals. It helps maintain situational awareness and simplifies the navigation process, allowing for more effective management of the aircraft's flight path.