Depending on the air bags... You "Air down" when lifting the rig, but read the fine manual because the key phrase is "Depending on the air bags"
I'm kind of happy to see the folks commenting on the lower cost Air-Lift, made in Lansing, MI, being better than the more expensive Firestones.
I know I was happy with the Air-Lift on my towed back when it led the parade insted of taking up the rear guard position.
That said.. Once I installed the bags on my towed and aired them up. WE NEVER un-inflated, ever, even when lifting the car on a frame lift.