In the AA forum:

http://www.flyertalk.com/forum/showt...84#post9578384

dstan mentions:
"You should, however, be able to check in for both outbound segments at PAP and check any bags all the way through to SJU."

This is regarding a question where the OP finds that booking 2 separate reservations (PAP - MIA, MIA -SJU) is cheaper than booking a single reservation (PAP - SJU) using the same routing through MIA.

dstan is saying we can check-in at PAP for our MIA - SJU reservation. Thereby saving the need to retrieve our checked baggage at MIA and recheck them for the MIA - SJU flight.

So, my question/curiosity is - What are the limitations to single point check-in?

A few examples:
I have a day trip - DEN - DFW in the AM. DFW - DEN in the PM (same day).
When I check in at DEN in the AM can I go ahead and check-in for the DFW - DEN flight at the same time (assuming I have no checked bags)?

Can I check in at DEN for a DEN - DFW flight that arrives DFW at 9:00AM on a single reservation? Spend the night in Dallas and go ahead and already be checked in at DEN for a DFW - MIA flight the following morning (with checked baggage)? I assume I wouldn't see my checked baggage until I arrived in MIA the following day.

I realise the motivation/likelyhood of someone actually things like this is highly debatable. I'm just curious if the system(s) actually allows it.