Boost your energy and immunity by exercising, and getting good nights' rests, on the days leading up to your trip.
This can be a bit tough if you're scurrying to pack luggage and secure your home at the last minute. Which is why you should start packing and prepping weeks in advance so you'll be way more zen en route to the airport.
Also, cut out dehydrating libations like coffee, caffeine, wine and liquor in the days leading up to your flight.
Drink lots of water instead.
Plus, I recommend drinking a glass of Vitamin C powder mix the day before and the day of your flight to boost your immune system.