Overlapping reservations
 

If I were to book 2 reservations on the same day, would AA cancel one or both of these? If only, would there be a rhyme or reason why one vs the other were canceled?

Does it matter if they are overlapping in time?

Does it matter if either/both are "fully refundable?"

I know Southwest has done this to me before automatically (i.e., one reservation is canceled), without notice, and without regard to which one was booked first, etc.

Yes, if it is physically impossible to take both flights. Sometimes they are slow to catch it, but one of them will likely be cancelled. You can probably delay the cancellation by not providing your FF no. for one of them.

And no, you will not get any notice.

Got it - thank you.