For me, the most intolerable thing about flying is lower-back pain. There's not much I — a 6-foot-3-inch man — can do to alleviate all of that, but I have found that decent lumbar support makes a huge difference in my comfort. Honestly, I'd turn around and go home if I arrived at the airport with my pillow. It may sound silly, but this little pillow is a travel must-have for me as I have broken my back twice in the past and am prone to flare-ups.
Lumbar rolls are easy to come by, but on budget flights they can take up half your carry-on space. Therm-a-Rest's Lumbar Travel Pillow is different though. It packs down way smaller than the competition and is plenty firm enough to support my back. Once I deflate and roll it up, I wrap an exercise band around it to keep it compact. An added bonus: I can use the band to stretch on arrival or during long delays.
On the other hand, shorter flyers, like my wife, might find discomfort arising from not being able to squarely rest their feet on the floor. You could put them on your bag, but that isn't always convenient or hygenic. My wife swears by this simple foot hammock, it is supportive, comfy, and very packable.
Therm-a-Rest Lumbar Travel Pillow, $29.95, at Amazon
Angemay Airplane Footrest, $9.99, at Amazon