An air leveling system uses the air suspension bags to do the leveling. In leveling mode, the system bypasses the ride height control valves and adjusts the height of the suspension airbags based on which way it needs to go to get it level.
My unit only has air leveling and I love it, like many of others. One of the things I like about it is the ability to raise the whole coach to go over high points without getting high centered or scraping things. Used that feature several times. We also spend a lot of time on the road and doing the truck stop / Walmart one-nighter thing. It's great not to have to worry about leaving jack impressions in the asphalt but still be able to be level. I've not yet encountered a campsite / parking lot where I've not been able to level it. I carry a set of leveling blocks just in case but have not had to use them yet.
1999 HR Navigator 42DSS
2008 Jeep Wrangler X Unlimited