I have a 2006 Navigator and 32 foot long 1994 Holiday Rambler Alumalite travel trailer.
The air suspension works fine, it even self levels when you hookup....but you need to do an adjustment the first time you hook up to the trailer....look in the Navigator owners manual.
The stock tires don't work that well pulling the trailer. They are too "soft?" and the Navigator didn't feel solid. I installed a set of Firestone Transforce HT (higher load and higher pressure) tires which really made a difference. I used to pull the trailer with a 2000 Silverado Z71, 1/2 ton pickup, with the higher pressure 1 ton truck tires, which was very stable. Prior to installing the Transforce tires on the Navigator, I thought I had really made a mistake buying it. After installing the Transforce tires, I am completely comfortable pulling the travel trailer. The Navigator also has a shorter wheelbase than my Silverado, which helps turning, etc.