Most planes nowadays have a charging port where you can plug in your phone for the duration of the flight. Therefore, I recommend getting an emulator on your phone and playing games on it. Usually if I want something casual, I get an NDS emulator and play Pokemon Platinum or HGSS. Other recommendations are FFIV, Etrian Odyssey III, Shin Megami Tensei, DQ4, some of these are ports but they run well on DS emulator.
Most planes nowadays have a charging port where you can plug in your phone for the duration of the flight. Therefore, I recommend getting an emulator on your phone and playing games on it. Usually if I want something casual, I get an NDS emulator and play Pokemon Platinum or HGSS. Other recommendations are FFIV, Etrian Odyssey III, Shin Megami Tensei, DQ4, some of these are ports but they run well on DS emulator.