1 & 2. Earplugs and a sleep mask - These long haul flights are the perfect opportunity to get a little bit of sleep if you can sleep on a plane. I personally can only sleep on a plane if I'm exhausted beyond belief. And even then a sleep mask works wonders, especially when people near you decide they really want to keep their window shades open and the sun is right in your eyeballs. Earplugs are a bonus.
PRO TIP: I usually pick a window seat on the side I sleep on. I sleep mostly on my left side, so I usually pick the left side of the plane. Something about doing that helps to trick my body into feeling like it's time to sleep.
3. Comfortable headphones - If you don't want to use earplugs, comfortable headphones are so important. If you're wearing your headphones for more than an hour or two at a time, comfort is really important! I recently got these Beats headphones, that I love! I'm a big earbud person, but a lot of people also love to wear the over ear headphones too.
4. Spotify Premium - I started using Spotify Premium when I was marathon training and needed access to hours of music that I could also access offline without purchasing 70 or 80 dollars of music from Apple. I love it for long haul flights because you can make a playlist of as many songs as you'd like and then you can make it available offline, meaning you won't have to use wifi or data to listen. This is awesome for flying or any other time when you might want to conserve data or battery life!
5. Mophie Charging Case for iPhone - Speaking of conserving battery life, I don't travel without a Mophie Charging case for my iPhone! Previously I had the external universal mophie charger, which I'd use with my regular phone charger, but I've found the charging case to be the most convenient and easy to use when you're traveling. You don't need to carry anything extra, the charger is on your phone! You just flip a little switch when you're low and it starts charging right then and there. Such a lifesaver for a flight on a plane that doesn't have power! I have this one. I thought it would be super bulky and I would hate it, but once you get used to it, it's just fine!
6. A zippered pouch - I think the key to staying organized when traveling is lots of compartments. There's not much I hate more than looking for something I need and having to dig through my entire cavernous carry on bag. I keep a smaller bag of some kind in my carry on with all of my in flight essentials (gum, dramamine, headphones, advil, lip balm, nyquil, etc) so that I can grab that and stick it in the seat back in front of me so I'm not digging through my carry on every time I need something.
7. Compression socks - I'm very pro wearing socks when I fly. If it's a shorter flight, I might wear sandals, but for long flights, I always wear socks, specifically compression socks. Long flights are always FREEZING, so socks are very important. Compression socks are great because in addition to keeping your feet warm, they also help keep your feet and legs from swelling due to cabin pressure and lower the chance you might get a blood clot.
8. Zabees Immune Support and Sleep powder - I discovered this stuff on a trip earlier this Fall and fell in love with it! When you're traveling, your immune system can always benefit from a little bit of a boost and the melatonin and other things in the powder also help me relax enough to drift off to sleep. I highly recommend this stuff before a red eye flight!
My last "must have" is a must have for ANY flight. It's TSA PreCheck. I signed up earlier this year and was mad I hadn't done it earlier, because it makes the process of getting through the airport SO MUCH SMOOTHER. You pay a one time fee and go to your local office to have them verify your identity and take your fingerprints and you get a known traveler ID that allows you to bypass the long TSA lines and go straight to the PreCheck line instead. I love it because I can keep my shoes and jacket on and I don't have to remove my laptop or liquids! I travel alone a lot and really prefer people not know I have an expensive laptop in my possession.