For anyone following this:
I have a 2011 XLT and began to get the Airbag Warning Light (AWL) early on, late 2011. I had it serviced numerous times over the years by Supreme Ford of Slidell who each time did a diagnostic and changed out, to the best of my knowledge, the seat-belt tensioner on the driver's side front. I can tell you that for the longest time, maybe six month, this was an on and off problem that had no correlation to anything (weather, time of day, temperature).
About two months back the light went on again, after being off for some time, and Supreme Ford changed, yes you guess it, the seat belt tensioner. That lasted about two weeks and I gave up. I opened a case with Ford and brought it to a new dealership, Veteran's Ford in Metairie, LA, where, yes, they changed the seat belt tensioner. That lasted until I got in the car to leave at which point the light went on again.
So, at this point, I began talking to the regional Ford Customer Service Rep and finally got Ford on board with the dealership to look beyond the seal belt tensioner at a potential wiring issue. I explained to them, if you had a lamp at your house and you were constantly changing out the light bulb with a new one after it failed, at what point would you consider the lamp?
So, the car went in yesterday and they are working on it now. They hoped to have it back last night, but not yet so hopefully that means they are digging into this and maybe once and for all I will feel confident about my air bag system.