I have read sources which suggest that the air on a plane is near enough sterile, as a result of the air con and air filtration system. As you say in order to be infected, you either have to be sat in very close proximity to an infected person, or come into contact with things they've touched. As people have their own tray tables, seats and meals etc, the only real way I see to spread the illness is through the lavatory (door handles, toilet seats).
For all intents and purposes, from what I see, you're pretty safe on a plane.
Originally Posted by: Bolty