My initial MSP-ORD flight was AA operated and AA marketed, thus I got 3 x 70 lb checked pieces. I didn't realize the weight limit was 70 lb but that was needed with all the camping equipment I was bringing with me
. Plus, since I was allowed 3 pieces and my friend who was flying DL had no free baggage, I took his piece of checked luggage too (my 2 pieces and his 1 piece).
When I checked in tonight, AS didn't bat an eyelash or even mention anything about charges when I said I was checking in three pieces. I didn't ask anything about why there was no charge - I just assumed they already knew I was allowed 3 free checked pieces due to the DOT rule mentioned above.
Thanks for all your replies.