The masks that have become ubiquitous in the streets of cities all over the world are now becoming the norm for travel, at least for a long time to come.
Face masks for flight crew have now been ordered by all the major U.S. airlines, and for passengers as well, except for Delta, which hasn't made it a passenger requirement yet. The largest union of flight attendants has called for a government requirement to insure a national policy.
U.S. airlines are not alone in implementing a mask policy as small steps are starting to revive the industry; many European and Asian carriers have done so or are likely to do so soon.
The cruise industry, which has also been talking about post-Covid travel rules seems likely to require masks for at least some activities. One line, Royal Caribbean, has gone so far as to design themed masks with its logo and to file trademark applications to name them 'SeaFace.'