For 15 years, I used to fly a lot for work, sometimes multiple cities in a week. I quit that kind of work a few years ago, and now travel only once every 3-4 weeks.
I’m sick (head and chest colds) way less now than I used to be. In fact, seems like the only time I get sick now is after travel (got the flu while traveling in December and it knocked me out for a week).
When flying, I use hand sanitizer a couple of times each hour, avoid touching as much as possible, and don’t touch my face. Helps, but can prevent everything. Eg when the flight attendant hands you that cup of coffee… who knows, maybe that’ll come with a 3-day head cold in addition to cream!