1. Open the overhead vent so that the air blows steadily in front of your face. 'What the heck' you say. This is first suggestion on the list because it's a must-do for me. I read this a few years ago, and since I started doing it I have not caught a cold from being on a plane (and yes that's a thing...wait til you read number 4). Here's the logic: lack of circulating air is one of the main reasons airplanes are breeding grounds for germs. Airplane air is actively recirculated and filtered. Take advantage of the clean air by using it to actively push away germs that may float into your personal space. Someone sneezed? Their possibly germ-infected droplets won't be able to find their way to your susceptible mucus membranes (eyes, nose, mouth) because the steady air stream steered them away. The cold air doesn't have to blow ON you; direct it so that it moves downward just past your nose and mouth. The little critters that float over from your neighbor won't stand a chance.
2. Disinfect your surroundings. Okay, I sound like a germaphobe here (is that so bad?). You've probably heard by now that the seat pocket and tray table are among the germiest (new word) places on the plane - sort of like stair rails and door knobs in public places. Handle a magazine, safety card, seatbelt hardware, or tray table knob after the passenger with pink-eye or runny nose and you might become the passenger with pink-eye or runny nose. If you carry a TSA-friendly container of hand sanitizer, great. Better, something specifically for surfaces. Don’t store personal items such as your water bottle, reading materials, or tissues in your seat back pocket; keep them stashed in your carry on bag. I've seen folks wipe down the seat, but since you're probably not planning to lick it, eat off of it or bury your face in it, that seems unnecessary.
3. If you practice number 1, and are sensitive to dryness, you might it helpful to also consider bringing a nasal mist to keep your nasal passages moist, which can boost your body’s germ flushing action. I know someone who applies a small amount of anti-bacterial ointment (like you might use at home on a small cut) just inside the nostrils (using a cotton swab or freshly washed hands!) Steam from hot drinks served on-board like coffee, tea or hot chocolate is another way to keep your mucous membranes moist.
4. Stay hydrated - applicable for your general good health anyway. These days, folks are rarely without their water bottles, so remember to keep drinking - even more so if you've consumed alcohol before or during your flight.
5. Avoid aisle seats. Sitting in an aisle seat may place you higher at risk of being exposed to germs, compared to other seat locations. The worst cold I ever caught on a plane was a direct result of sitting on the aisle. The fellow across the aisle turned his head to cough and did so directly on me. Yes, it can happen in any public place, but it happened on a plane so it's applicable to my story. He instinctively turned away from his neighbor and there I was two feet away and in the direct path of his cough. As I learned from my buddy Google.com, air expelled by a cough can travel as fast as 50 mph and carry almost 3,000 droplets, so I didn't stand a chance. Sneezes can travel up to 100 mph and create upwards of 100,000 droplets (hats off to the people who measure these things). Two days after the fateful cough I went down. Hard. It was a nasty cold, complete with cough (go figure). In an aisle seat you are also exposed to passengers who patrol the aisles for exercise or those coming and going to the restroom. People often tend to touch or hold aisle seats when walking up and down the aisles, contaminating them. It's not the hands per se; it's that people cover their coughing and sneezing with their hands, blow their noses into permeable tissues with their fingers, poke at their noses and eyes...you get it. Moving on...
6. Avoid airplane blankets and pillows unless they are packaged. Airlines wash blankets and pillows every 3 to 5 days, and usually, freshly washed blankets will only be set out for the first flights of the day. Customers who board toward the end of the day risk receiving blankets or pillows that have been used several times during the day. Eeeewww. Bring your own and launder it when you get home.
7. Consider carrying a face mask. Yes I know you'll be stared at if you wear it. In Asia, they are all the rage, both to protect the wearer from neighbors and vice versa. Haven't you ever traveled while sick? I bet you tried to make yourself inconspicuous, didn't you. Well, next time, protect your fellow travelers - they'll appreciate it. However, suppose you're healthy but find yourself on a flight where coughing and sneezing are ubiquitous. Although a face mask might not be your normal daily fashion choice, you'll be happy to pull out this one you've been carrying secretly for weeks and hoped you'd never need. All the otherwise healthy passengers will be totally jealous of your mask, wishing they'd had the foresight. Plus, they won't be able to see that smug expression on your face.
Let's not forget the most basic measures: wash/clean your hands, especially before you handle your food; avoid touching your face-parts with hands that aren't pristine, and if it's in your belief system and wellness plan get a flu shot. That last one is up to you, please don't write me back about it. When it's your turn to expel germ-laden droplets, please cover your mouth so that we remain friends. Stay healthy!
My disclaimer...I'm not a doctor and can't even play one on TV. Take my advice with a grain of salt, and use said salt in a warm-water gargle should you end up with a sore throat.