Originally Posted by
ThreeJulietTango
For award tickets, the original inventory must be available in order to SDFC. Assuming you're flying before February 2017, you would need Z availability on the earlier JFK-MIA flight. If it's not available, you may be able to standby for the flight regardless (AA's standby policy is frustratingly vague on this).
As an elite, you will be permitted to voluntarily separate yourself from your bag and it may go on the original flight.
I have had success requesting to standby for an earlier flight in Z at the FL (I assume that the AC can also do it) connecting from an international flight in Z. The agent listed me as standby for a seat in Z; I was first on the standby list and got the last seat in F (with a long upgrade list). Your mileage may vary.