Is it the air on airplanes that make people sick, or is it germs from passengers?
"air sickness" can be caused by many things. Anxiety about flying is common and fear of flying often develops in the 30+ age range. Mainly, this is because people finally have achieved stability in their job and home life, and feel like they don't have personal control on board the plane. This can often be overcome by simply taking a flying lesson, and learning what and who is controlling your destiny.
Physical illness can be brought on too, by ear and sinus changes that occur when air pressure changes. It can cause ear pain, and/or dizziness..which can upset a stomach. If you fly with a cold or sinus problem..it can definitey get you in trouble..
By nature of the dynamics of a closed in crowd, there are a lot of shared germs. Not only airborne ones, but on the seat handles, the pillows, and you don't even want to know what I've seen in lavoratories. Air is circulated, but not with germicides...so, as in any crowd..like in a concert venue...bring a small bottle of hand sanitizer, and your own blow up pillow...
And for pete's sake, DO NOT GO INTO THE LAVORATORY BAREFOOT1