The best investment I’ve made towards making air travel less hellish is the $4.00 I spent at Shoppers Drug Mart on a set of expanding foam ear plugs. I’ve been using them every since we flew to Thailand in 2002, and they’ve made a really big difference.
While it’s immediately obvious that airplanes are very noisy places, you can’t really get a good sense of just how noisy they are until you slip in the ear plugs. While they don’t cut out all the noise, they do successfully take it from “brass band playing in your head” to “somebody mowing the lawn across the street.” The effect this has on letting you stay relaxed (or at least “less tense”) and on letting you sleep is dramatic. Who would have thought all that “white noise” could be so stress-inducing.
Noise-cancelling headphones, or in-ear earphones like the Shure e2c can have the same dramatic effect, but they’re bulkier, more expensive, and mostly useful if you want to pump sound through them (although I have heard of people using the Bose headphones without any external audio source, simply to cut out noise).
I’ve also found the ear plugs useful for getting to sleep after long international flights in noisy hotels (although you have to make sure you can still hear your alarm clock!).
I recommend purchase of a little case of 4 or 6 ear plugs, as inevitably one or two get lost along the way. Insertion technique is important too: you have to compress them into a thin tube, and then slide them into your ear so they when they expand they made a snug sound-killing fit. This take some practice and the first few times they’ll likely expand right out of your ear.
For more on the flying experience and its challenges, see this post on Ian Williams’ blog.