I take long international flights. Just took one that was 15 hours for a single flight. If I get the first class seat where it lays flat then I usually sleep. Often I can't afford that and I can't sleep in tiny seats because I'm over 6 ft tall. I watch movies and play my steam deck. Usually both at the same time. As soon as I board I usually look at the movie selection and pick out the ones I want to watch and in what order and then I use that to gauge the time of the flight until landing.