I'm sure this has been asked before, but with good ole FT's search capability it's better to repost. I've never booked or flown with AA, always DL, but asking for a relative:

Have a roundtrip booked MEI-DFW-PHX-SEA-FAI and FAI-SEA-ORD-DFW-MEI. The flights between SEA and FAI are codeshare flights. AA flight number, but on AS metal.

For check-in purposes, will he be able to check in all the way at AA.com for outbound and bag checked all the way to FAI? And how will the return work? Obviously no AA counter at FAI so bag will be dropped off at AS counter.