Rip it out. It's a Jeep, lose the creature comforts dude, I took mine out........oh wait...........mine didn't come with airbags, sorry. :lol:
You could try a light misting of diluted bleach. Just don't leave it on too long, cause the bleach will discolor the cover.
Mold and mildew need moisture to grow, so somewhere you have trapped moisture in your Jeep. Possibly in the airbag compartment itself, especially if you do a lot of wheelin through deep water.
Hope this helps.