Drugs!

(No...not those kinds of drugs...)
I travel a lot, on business. One of the things I've learned to check carefully is the mini-medicine cabinet that goes with my shaving kit. Zantac75 for acid stomach, Immodium for the occasional bad hotdog or whatever, Sudafed 12 hour for the flights, tends to unstuff your head if you're moving through many time zones on different flights, and then something like Tylenol or Motrin for the muscle aches and headaches that are part of the game. I use Triptone for the boats if it looks like weather offshore, but some use Bonine successfully. You may have your own meds favorites, but I don't leave home without these anymore. These tend to be overlooked until you need them, but often (at least where I go) if you need them they are not available.
For irritating people on the plane, I second what Sue said about the earplugs - but I recommend instead of or in addition to the MP3 player, a pair of those noise-cancelling earphones. The best ones I'm aware of are made by Bose, but Brookstone (which is what I have) makes a decent pair for $100 less. There are others, but they tend not to be as effective (at least judging by my ears!) I've tried a lot of them, and the two I mentioned seem to be the most effective. They generate a wave pattern that cancels out the high pitched whine of the engines and much of the background noise on the planes. With a pair of earplugs in, the headphones on, and some soft music playing in the background, you can cancel out screaming babies sitting around you and other factors that tend to negatively categorize 8 or 9 hour (or longer) flights.
For the long delays, nothing beats a couple paperbacks that you pick up the week before and really anticipate reading. Also, snacks like nuts or jellybeans travel well.
Have a great trip.
Doc