Went to work and truck was fine. Came out to go home and front of truck was almost sitting down on the tires. Air shocks won't inflate. What causes this and what is the cost to fix. 2006 Lincoln navigator

Sorry to hear this. My advice would be to go ahead and say goodbye to your air suspension now before you repair anything else because that suspension is just going to continue giving you a headache. Here's a kit for your car. You can see how little it costs and know that even a novice DIYer can install this at home pretty easily. 2003 2006 Lincoln Navigator 4 Wheel Standard Air Suspension Conversion Kit...

Your air bags are leaking and sounds like your air compressor doesn't work. Suspect new air bags and a new air compressor. And/Or ride height sensor located at the drivers side fender well above the controll arm.

I would say that they could be leaking they use rubber for those and it can dry rot and crack i hate to say it but there not at all cheap-- instead some what expensive i would get a garage to have a look before bringing to dealer i hope this helps and also that it is something else for your wallets sake good luck to you