Can a copper face mask keep a person safe on an airplane while travelling?

Though copper does have anti-microbial properties (which is why you see drainage trays made of copper under water heaters) there is little to no evidence that it is any more effective than a 2-layer mask made of cotton. Plus manufacturers aren't very forthcoming about the amount of copper that is used. (Copper tends to be pricey.)

Best thing to do whatever mask you do buy, make sure it is fairly comfortable with an adequate fit and to wash it daily after use.

Er, no. Copper doesn't magically ward off viruses

safe from what?  Chinese weaponized flu?  Probably not.  The only way to be totally safe is to use a completely airtight plastic mask over your entire head and wrapped tightly around your neck.  Sadly if the flight is more than ten minutes long the mask will kill you   Other than that the KN95 is the best mask to take your chances with.

It works as well as a tinfoil hat!