Some tips
Glad to see so many other claustro flyers, but also feel bad for you all too. My own personal claustrophobia is people based. Being wedged in with other people is my key trigger, although small spaces are not great either. So being on a plane is a complete trigger for me. Strangely the door being closed doesn't trigger my claustro but having people stood up in the aisle, whilst boarding does.
Here's my survival guide for long haul flights, with claustro:
What Works
Aisle Seat
At least with an aisle you can look down the aisle, whilst having an attack, which makes it look like there's more room than there actually is. You can also over flow the side of your seat into the aisle a bit to give yourself more room.
Entertainment
The Nintendo Switch + Noise cancelling head phones are an absolute must. Even under a very bad attack, putting Mario on (which is about exploring a world) seems to trick my brain into believing there is more space. Similarly Zelda, with it's sprawling open world, is a good way of making me believe I have more space than I think. In fact, if distracted, I can deal with relatively severe claustrophobic situations because my brain doesn't get the chance to start the anxiety.
Space by the Galley
Often this is deserted and whilst it is quite small it can sometimes be enough of a change to make me feel that I have more room than possible. Although sometimes this can have the reverse effect and cause me to be more clausrtophonic if there are people hanging out there drinking / talking
Business Class
It costs a lot more but the extra space is worth it. However some business class has a screen relatively close to your face, which triggers my claustro. There is also a trend within business class to put you into a small, personal, booth which is worse for my claustro. Whilst I can see a lot of people like it, I hate it as I feel more enclosed.
Listening to music
This seems to stop my brain from wiring itself into a claustro state.
What Doesn't
Medication
I've only tried using Valium and because it dulls you, ironically, it makes me feel even more claustro. It's absolutely horrible, vile, stuff and makes me far worse. I've informed my wife, doesn't matter what happens, I am never to be given Valium or other similar meds.
Night Mask / Eye Cover
I find this makes things much worse. Because I can't see anymore I find that I feel even more enclosed. Closing my eyes generally replays whatever caused the claustro attack to start too (say I was having a claustro dream) so is very bad.
Walking around
Absolute worse is the toilet - this is highly enclosed and liking throwing petrol on the fire
Galley, if it has people in, can also cause massive problems for me.
Recent Attack
Recently on a long haul flight I woke up and had an attack. I got up and walked towards the galley. There was a flight attendant dosing in a chair and when he saw me he stood up and came towards me. This actually made things worse because now I had somebody in my personal space. He took me to an area in the Galley where they had snacks, I smiled politely, even though I was mentally collapsing and on fire. In the galley there was an older guy (50s?) talking to an air hostess. He was drinking a beer and it was obvious neither of them were moving any time soon. I really started to panic that the airline would realise my condition and maybe ban me from further flights which would cause massive issues for my business. I then walked around and found a seat, right at the front of the row, near the closed curtain. There was a sliver of curtain open and I could sit down and look through the sliver in the curtain. This allowed me to see more space than was obvious. I then put on my Nintendo Switch and around 30mins later the attack was gone and I was back to normal.