Before I get arrested by Icelanta, may i point out that all a FFP1 mask achieves is a reduction in droplets FROM the wearer. It doesnt stop aerosols, and after it is wet - which will be far less time than terminal to terminal - it is useless. Whenever the wearer touches the mask to adust it, rub their face, eat, drink etc etc they infect their hands. The vast majority of infection is from touching a surface someone else has touched up to 72 hours before. No airline can completely clean every part of the interior and if you watch pax boarding you see them touching every other seat, a couple of overhead locker, the toilets etc etc.
So masks and empty middle seats provide reassurance but little reduction in risk. What is important is the incidence in the countries the pax come from.....but after that it is pure luck as to whether one or more passengers is shedding, and if that is the case expect a significant cluster of cases. That is the science. Whether you can persuade people to fly is to do more with persuasion, reassurance and perceived need.