Underwear in your carry-on
Here is a tip you probably never heard: always carry extra underwear and extra socks in your carry-on. If you are stuck on a plane for over ten hours, you probably want to change before landing to feel fresher.
You won’t notice it, but your body sweats a little while sitting. During the long flight, your clothes will absorb the sweat, and you might smell funky. To feel clean and comfortable, carry a light change of clothes. No one likes sitting in sweaty, dirty clothes all day.