Because of costs, we have to overnight in ATL on our way from SFO. This is a 11:30 PM arrival and 9:45 am departure to ANU, taking the long way around the Caribbean to SXM. Do we have to claim our checked bags, as this is considered a connecting flight for fare basis purposes, or can (must?) we leave them with Delta?

They would already be checked through to SXM from your departure point. All you will have are your carry-on's.

Your best bet would be to check directly with Delta and probably do so upon check-in also.

Depends on the Airline. With AA if it's 12 hours or longer it has to be picked up and rechecked in for next days flight.

I agree with JD. Check with your particular airline, now, AND when you check-in, as often things change or the person you talk to on the phone seems not to know!

Thanks for the responses. I did a little further research and did finally call Delta who said I can check bags through for a 10 hour connection, and have the option of short checking and rechecking the bags. Apparently Delta allows up to 24 hours to check through bags via an international gateway. Too bad my flight isn't international enough to qualify for 1 free bag checked, but I would have 24 hours to through check.

We claimed our bag as I didn't want to leave it overnight but didn't have to. Coming back with no overnight it was tagged to go on the connecting flight to Toronto. It went seamlessly. Safe travels.