See invisibility is a handy 2nd level spell that says:
For the duration, you see invisible creatures and objects as if they were visible, and you can see into the Ethereal Plane. Ethereal creatures and objects appear ghostly and translucent.
Does this mean that someone affected by this spell can see air?
This question is academic, but inspired by seeing this setup where air becomes visible. However, some useful things that arise from seeing air are:
Quickly finding where the burning fuse of a pack of dynamite is
Seeing the pace of breathing of creatures, which is useful for insight
Knowing the relative warmth or coolness of things, as warm air rises and cool air sinks