Handling can be very variable, unfortunately. The intent is to get it to the destination, but the actual way they do that is occasionally a miss.

Example: recent SFO-LAX-MAD-BCN I class to celebrate our 45th anniversary, departing Monday:
Scheduled AA 1923 SFO - LAX. Cancelled.
EP Desk protected us on AA 2246 later in day (rain at SFO - poor augury!)
Got to SFO early, boarded earlier AA 1910, cancelled due to mechanical
Rule 240 to UA 867 (worst coach seats possible, old, worn A319)
Departed IB 6170 LAX-MAD (after 3 hours fighting IB personnel to board my wife)

Baggage delivered to our hotel in Barcelona on Saturday
(had arrived LAX on AA2246, which arrived weather delayed after IB 6170 departed, so in their infinite wisdom and commitment to customer service, bags boarded on next IB flight to MAD, Wednesday, which somehow gets us bags on Saturday - probably due to Good Friday holiday)
Boarded cruise Sunday

Normally we carry on only - for our 45th anniversary we figured "what can go wrong?" Hah!
AA's special concern for us (EP and Plat) - hah!