Melatonin is not recommended for lupus patients. You can read that on the Johns Hopkins lupus website. Take valerian root instead. Melatonin can cause flares.

Wear sunscreen and avoid sun coming in the window. You are closer to the sun in a plane.
Hydrate.
Get up and move around every half hour or at least every hour. If you can't get up, flex your toes, calves, and thighs.
Bring nutritious snacks (protein and complex carbs) to keep blood sugar even.
Bring a neck pillow so your head doesn't flop around if you fall asleep.
Bring earphones so you don't have to pay for them. Listen to your fav music in iPod or mp3 player.
I wear support knee socks, not the surgical kind, but they do have good support.

Make sure you take your pain medication and try to get up and move about a little to keep from getting stiff. God bless praying for safe travel for you. 💜💜💜
Love Eva Marie

Hello Brian
I made a trip to Italy 2 years ago
I took Zanax and had Pain meds for back up as per my doctor. Wear flight socks drink fluids and move around. Keeping the body relaxed is key during the trip....,

I also have an overseas flight coming up. My docs gave me the same advice. Before I was diagnosed I went to Greece and got dehydrated. Stage three kidney failure when I got home. So be sure to stay hydrated.

Make sure you take your meds, stay hydrated, and move around the cabin as much as you are allowed. I hope this helps