It's all about making the environment more Zen. (drug free)
So...
These are a must-have, IMO. The hours of jet engine droning is well attenuated by these things. The bad part of those headphones is if they rest up against anything in the droning plane, they don't work so well. So, a neck pillow may be helpful.
. . plug in some relaxing music, or an audio book on macro economic
Also take a Goretex type jacket/shell to throw over your head. --as a big part of air travel discomfort is the super-dry air. The jacket will help contain the moister of exhaling. Also to that end, Evian makes little aerosol cans of water.
Oh, and even if you don't get good REM sleep, your body will get some rest. ...so don't fret over not getting the usual REM.