[toohotatopic]

People come by plane. How do you travel by plane without risking infection?

Since it is not avoidable that at least one person on a flight is infected, you have to quarantine each passenger.

[divbzero]

The parent’s point rings true to me. It’s not so much the spread from country to country as it is the confined space that would concern me. As such, safety of domestic flights and trains should be considered as well.

[JabavuAdams]

Easier to trace who was on a plane with other infected people. You're not aiming to stop all infections, but to be able to slow, contain, and trace.