If you're far from the airport, it might be worthwhile to stay in a hotel (choose one with a heated pool) the night before.

I suggest pre boarding since you will get repeatedly jostled if you don't.

A down pillow is the best way to go IMO. Put your pillow in your carry on bag and only carry on things that are essential for the flight. Slipper socks, wear layers in case you get chills or too hot, bring a soft throw, meds, healthy snacks with protein, an e-reader or tablet to watch movies to distract you, and headphones ready to go with mellow music if you're sensitive to sound.

Lidoderm patches that are precut or Lidocaine cream are a good idea IMO. I also start a course of steroids a few days before flying which makes recovery time much less--a few days as opposed to several for me (with shorter flights).

DO NOT take sleeping pills like Ambien when flying--it just isn't safe.

As soon as you arrive, take a bath with Epsom salts asap. You could even pack a compress for the plane even.