This simple, inflatable pillow provides the lower back support I wish a coach airplane seat would.
Airplane seats are the enemy of your lumbar lordosis, or that little curve at the base of your spine. Spending too long in a sky-high torture device without this simple pillow leaves me limping for hours, or days. At $12, I keep one in each of my likely travel bags.
Simply putting a few puffs of breath into this comfort enabler at ground level allows it to expand quite nicely, and apply just a little pressure to my lower back at normal cabin pressure. Its kinda fun to use the pillow to conduct simple air pressure and volume experiments with as well. Deflating this before landing will leave it super compact under normal air pressure.
I don't fly without my McKenzie Airback.