One time I flew from LHR-LAX. This was late autumn. We took off at about 15:30. The most direct route took the plane northwards over Greenland for a couple of hours before we started heading southwards over Canada and the Rockies.

About an hour into the flight, the sun set. I had a window seat and distinctly remember seeing nighttime over Greenland, and only being able to make out lakes and ice (black and white) and nothing else.

An hour or so after sunset, the plane started heading southwards. The horizon became red again, and then the sun came back up. It stayed up above the horizon for another hour or so before setting again.

Never in my life have I before or since seen a reverse sunset - and I don't expect I ever will again. Truly the coolest experience I have ever had whilst flying.