Most of my longer trips are in darkness but today I had the rare luxury of a daytime flight. The December sun inevitably dropped away towards the end of the journey, but took a curiously long time to slip into the clouds. I find planes oddly serene oases in a busy life and watching a lingering sunset is a rare joy. After the sun had set, the horizon developed solid strata of light, its colours slowly deepening and changing over time; a perfect rainbow, hammered flat by the unfelt speed of the plane.