Asked by: Terry Fairhall, By Email
The main reason is that it protects the aircraft from the effects of solar radiation. Aircraft struggle to stay cool while loading and unloading passengers at airports in hot countries, and brilliant white paint helps bounce back some of the sunlight. It also helps protect aircraft parts made out of composite materials from damage through ultraviolet radiation, which is substantially higher at altitude.
Robert is a science writer and visiting professor of science at Aston University.