I had an AWD automatically entered when I made my latest reservation. A460200. It gave a better than usual weekday at DTW. I tested the regular rates and they were cheaper than usual, albeit higher than this rate.

The only difference that I can think of is that I entered US Air as my arriving carrier, but I doubt that it is clever enough to then generate a US Air related discount. A long time ago I had the National Motorists Association in my profile and it started with A but I haven't kept track of that number.

Could it have been cheaper because I returned on Friday evening? It was only $44 after all the taxes and fees.