There is an 'official' UA fragrance - 'Landing.' Delta (who started this...) calls it 'Calm.'
They use it in the hot towels (I recognize it there) and according to the report below from 2015 in the clubs - not sure how they actively add it to the cabins other than the lavs. There used to be a scent disc in the lavs but I think they cost cut that into the new soap dispenser that has that plastic stick, which is supposed to be a freshener.
The article below says having it diffused in the cabins isn't a thing
"Putting atomized diffusion machines on aircraft seems to be a no-fly zone, carriers say, because it raises licensing and inspection issues with safety regulators."
https://www.wsj.com/articles/airline...ard-1422832562
"United is just beginning to introduce its fragrance,
a medley of orange peel, sandalwood, cedar and leather, developed by a Charlotte, N.C. scent marketing firm called ScentAir. Landing has landed at a few locations at United’s O’Hare Airport hub in Chicago, including airplane boarding bridges. On a recent morning, a diffuser machine had just been installed on the wall near a potted plant in the lobby of one of its four United Club lounges. Marlene Tolbert, a supervisor in the club, says she thought it was “a pine smell for the holidays.” But her colleague Linda Chrobak disagreed. “I can smell the orange,” she says.
"