I regularly take 11-14 hour flights and have collected a veritable arsenal of tools and tricks to ensure I'm in the best shape possible when I arrive.
If you're really, really sure you can't sleep on a flight, the only choice is to try and do something else in that 20 hours, and make sure there's a nice dark hotel room waiting for you at the other end. But otherwise, I am going to assume you are still hoping to get a few winks in.
First up, booking:
- If at all possible, book an evening flight, so you have a chance of going to sleep at or later than your normal time. It's much easier to fix your sleep cycle after you've arrived in your new timezone.
- If you can't afford business class, consider premium economy which gets you more recline and more legroom. Failing that, I've noticed that on many jets the first row behind premium economy still benefits from the extra legroom.
- When picking your seat, be careful to avoid the front/middle row where you run the risk of being in front of a bassinet containing a screaming baby.
- Avoid being near the toilet, and unless you expect to make more than one visit yourself, get a window or central seat, so that you don't need to be woken up when your neighbor has a call of nature.
- Even if you don't have special dietary requirements, consider ordering a special meal. It will usually be served earlier (so you can concentrate on getting to sleep) and as a bonus, will often be better quality due to being specially prepared.
- A high-quality sleep mask such as a HiberMate - ideally something that shuts out all light without putting extra pressure on the eyes.
- Disposable foam ear plugs. Careful if you buy these in the airport - some ear plugs are just for protecting against fast air pressure changes and don't block sound.
- Noise-cancelling headphones. I use Bose QuietComfort, although you may prefer in-ear headphones. Make sure you have an airplane kit and spare battery if applicable. (Side note - I just added a Fiio E6 headphone amp to beef up my Bose set.)
- Music. Noise cancellation doesn't necessarily get you silence on a plane, but ambient electronica, jazz or classical music will help to relax you and drown out distractions. In a pinch, most flights will provide an appropriate music channel, but I prefer to pick my own.
- Extra layer of clothing - a thin blanket and usually a pair of socks will be provided, but that won't be enough if you're getting on the plane in a hot area wearing just a T-shirt, make sure you have a jumper and jacket on hand as they tend to keep the temperature low.
- Flight pillow. I don't actually carry one of these, but perhaps the extra bulk would be justified if I found one that works for me. As it is, I just rely on the small pillow they provide - but check below for tips there.
- Sleeping pills: I don't actually recommend sleeping pills but I will comment. Ideally you want natural sleep. The best way to achieve that is with darkness, silence, cool and comfort. If you've found you're able to get a good night's sleep using pills in the past though, there's no reason not to have them on hand.
- Melatonin: this is a little different from sleeping pills. If you are getting your flight at an odd time of day but hope to sleep anyway, melatonin can help to tweak your sleep cycle, but again only in concert with darkness, silence and comfort.
- Snacks: apart from the food advice above, I generally don't rely on airline food. I always travel with a nut mix, some dark chocolate, and any fresh snacks I have time to grab on the way.
- Wear loose-fitting clothes.
- Limit yourself to one alcoholic beverage. It seems like a waste to not take advantage of the free-flowing booze, but it's not going to help you sleep unless you actually manage to drink yourself unconscious (not recommended). These days, I just drink water and green tea on the plane - I feel better when I wake up, and diuretic effects are avoided.
- Skip the in-flight movies. Again, seems like a waste, but it doesn't help you sleep. Unless it's The Tourist, or any recent Eddie Murphy flick.
- Take off your shoes, and put the socks on. Your feet will swell up a little during a long flight, making shoes uncomfortable.
- The main thing you need is darkness - get your mask ready.
- That tiny pillow they provide isn't for your head. Instead, use it to cushion your lower back - that alone might solve your problem sleeping in chairs.
- Recline your seat and adjust the headrest - don't forget to pull up the 'ears' on the side as they'll help to hold your head in place as you sleep.
- Cover yourself with the blanket as best you can and fasten your seatbelt over the top.
- Depending on noise levels and your mood, use the ear plugs or the headphones. I usually start with headphones and go to ear plugs (which I find a little uncomfortable) if necessary.
- Pull down your mask and shut your eyes. Concentrate on your breathing. Don't get anxious if you can't fall asleep quickly, give it at least 20 minutes or so.
If after all that you still can't sleep, it's time to hit the movies and booze...