It is time to shut these ships down for the time being. There are so many ways this virus can spread. And it sounds like it might even get carried by the ventilation systems. If that is the case then it does no good to lock people in their rooms.
Airplanes will have the same problems. There may be no such thing as isolating passengers on an air plane. That batch that came back to the military base for Quarantine were transported on a commercial flight with unaffected passengers. The word is that they were isolated. The truth is that everyone on the plane may have been exposed due to the ventilation system. And I doubt that the normal passengers had a clue who was on the plane.
If you are referring to the Diamond Princess flights, I believe they came back on two special chartered 747 cargo converted to passenger, with special quarantine setup. No regular commercial passengers exposed. Somebody somewhere in in US Gov surprised me.
Our neighbors just returned from a month long cruise (Australia/New Zealand) ...going to avoid them for awhile
I do not think the Diamond Princess will ever be safe for travel.
Once the passengers are off, they should sink it.