10 Things: to pack in your carry-on luggage for a long flight

1. All your "essentials": passport, money, travel details, phone etc
2. Lip Balm - lips always seem to dry out on long flights
3. Individually wrapped packets of antibacterial wipes for wiping down your seat area (buckle, tray, remote, light switches, TV etc) and for after meals and using the bathroom
4. Just one good book, flying is actually the best time to relax and rest so try not to overload yourself with too much to do on the flight. Enjoy the downtime, put a movie on or some music and close your eyes.
5. Socks - especially if you are wearing open shoes on the flight. There is nothing worse than cold feet on a long flight and these days with all the budget restrictions, few airlines provide the complimentary socks of yesteryear.
6. A small "essentials" kit that will contain ibuprofen, bandaids, ear plugs, toothbrush and paste, comb.
7. GasX. Everyone gets gassy in the altitude. That doesn't mean it's OK to fart as you please. You are still sharing confined air space with scores of others
8. Spare Underwear and light clothing.  Believe me, I never thought I would use it until I got stranded in Miami airport for many, many hours before the airline finally decided to put us up for the night in a hotel (without our luggage), which took an hour to get to as it was in the middle of an Indian Reservation. Oh, yes it was a casino/hotel/Indian Reservation - what a great combination.  Luckily, I had my toiletry bag with me and was able to take out my contacts, brush my teeth etc And I was so glad to see my two sets of spare knickers! It was at least a full 24 hours later before we were on another flight. It happens.
9. Something small (and non-perishable) to eat just in case. i.e. a small trail mix packet or a bag of chips
10. Don't forget your moisturizer. A small hydrating lotion is plenty, don't bring along your big bottles!!! In fact, just pump a little into an inexpensive refillable bottle that you can buy from any drugstore for a few dollars. It will be easy to throw out or leave behind if you have to.