I've heard it twice now.
I loved to fly places, before it became such an impossible hobby.I would always get a respiratory infection when I'd fly. A wise friend told me to drink lots of water for 24 hours before I went on a trip. The recycled air, full of virus, can't be avoided but if you have well hydrated sinus those virus can't attach to you as easily.
Now a couple of nurses I know told me to drink extra water
when I'm going to be around the sick grand kids.
Guess why? Yes the virus's can't get you as easily if you are "wet" inside.
So it can't hurt can it?
Drink some extra water when you know you will be around crowds, little kids, etc.
Besides if you are one of the Spark people you are trying to get your eight cups a day anyway!