Unidentified shape near airportMyself and another employee at the airport just happened to be looking at an arriving aircraft on a 1 mile final to runway 15 at ADS. Behind that aircraft we observed what looked like another aircraft making what appeared to be an "S" turn for spacing on final. Immeidately I knew it wasn't another aircraft as it had no real distinct shape other than a mass. I thought for a moment that it might be a bird, but I watched it for another minute and that is when it really got my attention. Not knowing the "shape" or size of the object I couldn't tell how far away it was but after a left to right movement, it just stopped. It was a dark mass with no real edges. It almost seemed like an extremely large piece of ash. We watched it for another minute and it did not move again. It just sat stationary out there on the final for the runway. I was very intriqued but work called. About 5 minutes later I returned to see if it was still there, but it was gone.((NUFORC Note: Date of sighting may be approximate. PD))