I've never gotten sick from a flight, including marathons like Atlanta-Johannesburg and Los Angeles-Sydney. Am I just lucky???

Acidophilus might help deal with intestinal bacteria, but won't do anything about viruses, including all those respiratory ones.

I have nothing to add to the above list, except to second the recommendations for staying hydrated, washing hands and surfaces that you'll touch a lot (remotes, airline tray tables, etc.) since if they ARE "cleaned," it's often done with a questionable rag that removes visible dirt only.

As I told my kids when they were arguing about not washing their hands when we got home from the mall: Assume that everything YOU touched was also touched by some little kid who picks their nose.

I travel every week and never get sick, just tired. I never use all the antibacterial stuff and take virtually no precautions. I eat tacos off the street in Mexico, too. Years ago I worked in an elementary school and the new teachers would get sick many times during the first year of teaching. They had to build up immunity during that first year. Elementary schools are just as gross as planes or hotels... possibly worse.
Sometimes you are doing more harm than good by overdoing all the antibacterial products. I just wash my hands a lot.

Actually: I have read summaries of research on contagious respiratory diseases: the main way they are transmitted is your hands to your face -- so -- yes keep cleaning your hands and also avoid touching your face or your food. (to me cleaning hands seems more important than cleaning stuff you will touch. But -- I guess I got a big enough variety of diseases as a kid to be immune to most of these things).

The idea behind cleaning things that you will touch is that there are some things that you touch a lot, that other people also touch a lot, that you just can't wash your hands after every time you touch them -- these include airline tray tables and various parts of your hotel room, especially doorknobs and remotes.

I think I'm pretty moderate on this issue, considering that my Mom carries alcohol wipes with her and always cleans things like restaurant silverware before using it.

I've never gotten sick after a flight. I chalk it up to getting plastered on the flight. I think the alcohol kills all the germs.

Just kidding.

Geesh, I thought I was the only germo-phobic person who carried their trial size packets of antibacterial cleaning and hand wipes to hotel rooms. I'm sure meant to be covered in above, but I didn't see mentioned, but first thing I wipe off in hotel room is the toilet seat and the vanity/faucet. The downside to the anti-bacterial gels is that we are becoming too dependent on them....they also kill good bacteria with the bad, so in some ways, doing us harm instead of good.

Anonymous and Elizabeth win the prize(s) for most correct answer.
Studies have shown that the vast majority of post-flight infections are caused by: people dragging their dirty hands up to their mouths/noses and depositing bacteria/viruses there.

I fell victim a couple times several years ago (partially ruined a trip to Europe) and vowed never to have this happen again.
I've been extremely careful on planes (and in airports) ever since and have had zero problem.

The trick is to imagine how dirty your hands become as you touch your arm rest, magazines etc and never allow them to touch your face until cleaned.
So before eating, wash them carefully.
Don't put your fingers in your eyes/nose/mouth and you'll be amazed at how much better your post-flight health will be.

As for Vitamin C, it's not been proven to help prevent such infections, and the data on Echinacea is conflicting (some studies say it helps, others show no benefit).
And hydration is always important on flights over an hour.

While I agree with all the contaminated- hands-from-surfaces-to-face theories, I have to believe there is something additional at work here - we all touch equally contaminated surfaces closer to home. For me, it may be that I often start vacations overtired, overstressed and on vacation am not as nutritionally careful as I am at home. (Fewer fruits and veggies, etc.). Perhaps that combined with the surface contaminants. That said, we flew 12 hrs each way to Egypt, touched all sorts of bacteria-laden surfaces (some of the bathrooms we used were beyond description in their grossness) and none of us got sick.