For years, I was stuck holding my tablet/phone when watching movies and tv on flights or train rides. Not only did this mean I was getting a sore neck staring down (instead of straight ahead) for hours, but it also meant that my hands were busy and took multi-tasking off the table. Those days are gone!
I’ve only been on one plane with tablet stands in the seats (Lufthansa A321neo), but the iFlex stand allows for comfortable watching just about anywhere. It’s a bendable neoprene rectangle that can be bent to fit your device and put behind tray tables, in-seat screens, on tables, etc. Since it folds flat, it takes up almost no space, and mine is still going strong after three years. I don’t travel without it.