droplets and airborne is a somewhat arbitrary distinction pulled out of .. thin air.
https://www.wired.com/story/the-teeny-tiny-scientific-screwu...
Whether the droplet/aerosol float through the air has to do with much more than particle size.
"There was just one literally tiny problem: “The physics of it is all wrong,” Marr says. That much seemed obvious to her from everything she knew about how things move through air. Reality is far messier, with particles much larger than 5 microns staying afloat and behaving like aerosols, depending on heat, humidity, and airspeed."