Don’t know if this is a reality, but it seems like in this day and age, planes would/should carry surgical masks for the passengers in case a person on board is found to be contagious with a serious disease, while the plane is inflight.
I know in our doctor’s office there is now a sign requesting anyone who’s coughing or may be contagious to ask the front desk for a mask to wear in the waiting room.
I do wish that they had the masks and, like the Doctor's office, if a passenger is coughing repeatedly they should be asked to put on the mask.
I was on a flight yesterday and the girl next to me was coughing and coughing the whole flight.