It is possible to happen, although not many. During flying, we are in this airtight environment, which makes it easier to get infection through virus, bacteria and dusts in the air. Because bacterial and viral conjunctivitis are very contagious, so getting infected in plane is possible. If you are wearing contact lenses, it might cause infections through long time journey. But the low air pressure during flight in the plane, especially the takeoff and landing, could cause sinuses. Because of the reduced air pressure, it can cause pressure build up in head, which result in severe pain in temple and eyes. If you need to travel by plane, and you happened to have this kind of situation before, I suggest you to note some points. First of all, you'd better not wear contact lenses. It might be painful in the flight of your eyes, and wearing contact lenses could make you feel worse. Take some eye drops and sinus drops with you just in case.
