Why is the F2 region mainly responsible for the longest distance radio-wave propagation?

The F2 region is the highest layer in the ionosphere, typically sitting between 250 and 400 km above the Earth's surface during the day. Because of its high altitude, radio waves refracted back from the F2 layer travel a much longer distance across the curvature of the Earth before striking the ground compared to waves refracting from lower layers. This geometry provides the maximum possible 'skip distance' for a single hop. Distractors suggesting it is the lowest region are factually opposite. The idea that it exists only at night is also wrong; the F layer actually splits into F1 and F2 during the day. While the F region does absorb fewer radio waves than the D region, its sheer altitude is the primary geometric reason it facilitates the longest distance communications.