The last thing you want to take on vacation is a bug from your flight. So:
Keep cabin time short. Book early-morning flights, when you're least likely to get stuck in a traffic jam on the runway.
Avoid crowded flights when possible, since more people equals more germs. The lightest travel day is Monday; the heaviest, Thursday.
Bring your own stuff -- blankets, pillows, and reading material -- to avoid sharing germs. (Anything that comes in a sealed bag is fine, though.)
Don't drink the water, or brush your teeth with it. Whether it's from the bathroom sink or a pitcher on the drink cart, it's often infested with bacteria, says Philip Tierno, Ph.D., director of clinical microbiology and immunology at New York University Medical Center. Stay hydrated with canned or bottled beverages.
Pack alcohol-based hand sanitizers, and use them often.