Originally Posted by Often1

Not only does pre-flight testing help on the quarantine front, but it also helps in that positive passengers are not boarded at all and thus do not spend any time cooped up with however many other passengers there are on the flight. While there will be, at least for the time being, false negatives, this is also a way to help carriers return to profitability by filling aircraft. If one need not worry about being infected by other passengers, no need to block seats and that will permit a return to normalcy.