1) Sip warm water throughout the entire trip. Travel with a thermos. Any time you can, fill it with hot water. Bring some lemon and lime pieces with you if you need a little flavor (but don't drink lemon/lime water the entire time, too much citric acid is hard on the enamel of your teeth). Flying (and driving) is very dehydrating and dehydration makes you more susceptible to headaches, dry nose, jet-lag and catching a cold/flu.
2) Stay away from: sugar/candy, cold foods and icecream, soft drinks, and dry snack foods like chips, peanuts and crackers. All these things have either dry, light or cold qualities and the sugar creates a breeding ground for germs. You need more grounding and rich foods when you fly. So find some oatmeal, soup or a a hot sandwich. Better yet, bring some of your own food to snack on like home made muffins with almond butter, veggie and fruits slices, steamed greens with ghee etc. By eating these warm, heavier, nourishing food you will feel more grounded and settled. Stay away from fast food!
3) When you land at your final destination, drink a cup of warm milk (almond or organic whole milk preferred) with a dash of cinnamon, cardamon, ginger, turmeric and a teaspoon of Ashwagandha powder. Ashwagandha is very grounding, calming, nourishing and building to your nervous system, which has been depleted and rattled from flying or driving. You can purchase capsules or powder here. Make up the spice mix before you leave home and carry it with you so you have it right away. If you can't have the warm milk right away, drink it before you go to bed that evening.
4) Get outside as soon as possible and take a 10 minute walk. Fresh air and sunshine will help to settle your nerves and system and help the body come back into its element.
5) Get in the time zone ASAP. Try not to take a nap, go to bed when night time comes, that way you can wake up around the same time as everyone else and get into the grove quicker.
All tips apply for car and plane travel.