Let's talk about airliner cabin air.

[wnylib]

58. Plus the flow of air through the cabin.

Even if the air is "pure" at the point of origin and after going through a filter, there is a period of air flow through the cabin. A cough or sneeze causes some amount of virus to enter the air, where it can remain active for 3 hours.

Carry on bags sit in a rack, touching each other. Passengers touch nearby bags in the process of loading and unloading their own. People touch the arms and backs of the seats as they walk to their own, and as they walk to the bathroom and back. If not with their hands, their clothes brush aginst people and seats as they pass by.

The virus is active on plastic and metal surfaces for 3 days, so any surfaces inside the cabin could have active viruses on them from previous flights up to 3 days before.

If the middle seat is left vacant, there still are not 6 feet between passengers in the same row. And what about the distance between rows ahead and behind you?

Only a really urgent crisis makes air travel worth the risk. (I know that "really urgent crisis" is redundant, but the word "crisis" alone can be too loosely interpreted.)